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ADOPTS WITHOUT AMENDMENTS:

International Fuel Gas Code 2009 (IFGC 2009)

Heads up: There are no amended sections in this chapter.
This chapter shall govern the installation, maintenance, repair and approval of factory-built chimneys, chimney liners, vents and connectors and the utilization of masonry chimneys serving gas-fired appliances. The requirements for the installation, maintenance, repair and approval of factory-built chimneys, chimney liners, vents and connectors serving appliances burning fuels other than fuel gas shall be regulated by the International Mechanical Code. The construction, repair, maintenance and approval of masonry chimneys shall be regulated by the International Building Code.
Every appliance shall discharge the products of combustion to the outdoors, except for appliances exempted by Section 501.8.
Masonry chimneys shall be constructed in accordance with Section 503.5.3 and the International Building Code.
Chimneys and vents shall be sized in accordance with Sections 503 and 504.
Abandoned inlet openings in chimneys and vents shall be closed by an approved method.
Where an appliance equipped with a mechanical forced draft system creates a positive pressure in the venting system, the venting system shall be designed for positive pressure applications.
Connection of appliances to chimney flues serving fireplaces shall be in accordance with Sections 501.7.1 through 501.7.3.
A noncombustible seal shall be provided below the point of connection to prevent entry of room air into the flue. Means shall be provided for access to the flue for inspection and cleaning.
An appliance shall not be connected to a flue serving a factory-built fireplace unless the appliance is specifically listed for such installation. The connection shall be made in accordance with the appliance manufacturer's installation instructions.
A connector shall extend from the appliance to the flue serving a masonry fireplace such that the flue gases are exhausted directly into the flue. The connector shall be accessible or removable for inspection and cleaning of both the connector and the flue. Listed direct connection devices shall be installed in accordance with their listing.
The following appliances shall not be required to be vented.
  1. Ranges.
  2. Built-in domestic cooking units listed and marked for optional venting.
  3. Hot plates and laundry stoves.
  4. Type 1 clothes dryers (Type 1 clothes dryers shall be exhausted in accordance with the requirements of Section 614).
  5. A single booster-type automatic instantaneous water heater, where designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the heater is installed in a commercial kitchen having a mechanical exhaust system. Where installed in this manner, the draft hood, if required, shall be in place and unaltered and the draft hood outlet shall be not less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from any surface other than the heater.
  6. Refrigerators.
  7. Counter appliances.
  8. Room heaters listed for unvented use.
  9. Direct-fired makeup air heaters.
  10. Other appliances listed for unvented use and not provided with flue collars.
  11. Specialized appliances of limited input such as laboratory burners and gas lights.
Where the appliances listed in Items 5 through 11 above are installed so that the aggregate input rating exceeds 20 British thermal units (Btu) per hour per cubic feet (207 watts per m3) of volume of the room or space in which such appliances are installed, one or more shall be provided with venting systems or other approved means for conveying the vent gases to the outdoor atmosphere so that the aggregate input rating of the remaining unvented appliances does not exceed 20 Btu per hour per cubic foot (207 watts per m3). Where the room or space in which the appliance is installed is directly connected to another room or space by a doorway, archway or other opening of comparable size that cannot be closed, the volume of such adjacent room or space shall be permitted to be included in the calculations.
Connectors shall connect to a masonry chimney flue at a point not less than 12 inches (305 mm) above the lowest portion of the interior of the chimney flue.
Appliance connections to a chimney or vent equipped with a power exhauster shall be made on the inlet side of the exhauster. Joints on the positive pressure side of the exhauster shall be sealed to prevent flue-gas leakage as specified by the manufacturer's installation instructions for the exhauster.
Masonry chimneys utilized to vent appliances shall be located, constructed and sized as specified in the manufacturer's installation instructions for the appliances being vented and Section 503.
Flue lining systems for use with residential-type and low-heat appliances shall be limited to the following:
  1. Clay flue lining complying with the requirements of ASTM C 315 or equivalent. Clay flue lining shall be installed in accordance with the International Building Code.
  2. Listed chimney lining systems complying with UL 1777.
  3. Other approved materials that will resist, without cracking, softening or corrosion, flue gases and condensate at temperatures up to 1,800°F (982°C).
Flue lining systems for use with Category I appliances shall be limited to the following:
  1. Flue lining systems complying with Section 501.12.
  2. Chimney lining systems listed and labeled for use with gas appliances with draft hoods and other Category I gas appliances listed and labeled for use with Type B vents.
The design, sizing and installation of vents for Category II, III and IV appliances shall be in accordance with the appliance manufacturer's installation instructions.
Where an appliance is permanently disconnected from an existing chimney or vent, or where an appliance is connected to an existing chimney or vent during the process of a new installation, the chimney or vent shall comply with Sections 501.15.1 through 501.15.4.
The chimney or vent shall be resized as necessary to control flue gas condensation in the interior of the chimney or vent and to provide the appliance or appliances served with the required draft. For Category I appliances, the resizing shall be in accordance with Section 502.
The flue gas passageway shall be free of obstructions and combustible deposits and shall be cleaned if previously used for venting a solid or liquid fuel-burning appliance or fireplace. The flue liner, chimney inner wall or vent inner wall shall be continuous and shall be free of cracks, gaps, perforations or other damage or deterioration which would allow the escape of combustion products, including gases, moisture and creosote.
Masonry chimney flues shall be provided with a cleanout opening having a minimum height of 6 inches (152 mm). The upper edge of the opening shall be located not less than 6 inches (152 mm) below the lowest chimney inlet opening. The cleanout shall be provided with a tight-fitting, noncombustible cover.
Chimneys and vents shall have airspace clearance to combustibles in accordance with the International Building Code and the chimney or vent manufacturer's installation instructions.
Exception: Masonry chimneys without the required airspace clearances shall be permitted to be used if lined or relined with a chimney lining system listed for use in chimneys with reduced clearances in accordance with UL 1777. The chimney clearance shall be not less than permitted by the terms of the chimney liner listing and the manufacturer's instructions.
Noncombustible fireblocking shall be provided in accordance with the International Building Code.
All vents, except as provided in Section 503.7, shall be listed and labeled. Type B and BW vents shall be tested in accordance with UL 441. Type L vents shall be tested in accordance with UL 641. Vents for Category II and III appliances shall be tested in accordance with UL 1738. Plastic vents for Category IV appliances shall not be required to be listed and labeled where such vents are as specified by the appliance manufacturer and are installed in accordance with the appliance manufacturer's installation instructions.
Connectors shall be used to connect appliances to the vertical chimney or vent, except where the chimney or vent is attached directly to the appliance. Vent connector size, material, construction and installation shall be in accordance with Section 503.
The application of vents shall be in accordance with Table 503.4.
Where vents pass through insulated assemblies, an insulation shield constructed of steel having a minimum thickness of 0.0187 inch (0.4712 mm) (No. 26 gage) shall be installed to provide clearance between the vent and the insulation material. The clearance shall not be less than the clearance to combustibles specified by the vent manufacturer's installation instructions. Where vents pass through attic space, the shield shall terminate not less than 2 inches (51 mm) above the insulation materials and shall be secured in place to prevent displacement. Insulation shields provided as part of a listed vent system shall be installed in accordance with the manufacturer's installation instructions.
Vent systems shall be sized, installed and terminated in accordance with the vent and appliance manufacturer's installation instructions and Section 503.
All portions of vents shall be adequately supported for the design and weight of the materials employed.
In concealed locations, where a vent is installed through holes or notches in studs, joists, rafters or similar members less than 11/2 inches (38 mm) from the nearest edge of the member, the vent shall be protected by shield plates. Protective steel shield plates having a minimum thickness of 0.0575 inch (1.463 mm) (No. 16 gage) shall cover the area of the vent where the member is notched or bored and shall extend a minimum of 4 inches (102 mm) above sole plates, below top plates and to each side of a stud, joist or rafter.
This section recognizes that the choice of venting materials and the methods of installation of venting systems are dependent on the operating characteristics of the appliance being vented. The operating characteristics of vented appliances can be categorized with respect to: (1) positive or negative pressure within the venting system; and (2) whether or not the appliance generates flue or vent gases that might condense in the venting system. See Section 202 for the definitions of these vented appliance categories.
Except as permitted in Sections 503.2.1 through 503.2.4 and 501.8, all appliances shall be connected to venting systems.
Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications (see Section 503.3.4) and to vent industrial appliances, such as where the process itself requires fume disposal.
Where located in a large and well-ventilated space, industrial appliances shall be permitted to be operated by discharging the flue gases directly into the space.
Listed direct-vent appliances shall be installed in accordance with the manufacturer's instructions and Section 503.8, Item 3.
Appliances incorporating integral venting means shall be considered properly vented where installed in accordance with the manufacturer's instructions and Section 503.8, Items 1 and 2.
A venting system shall be designed and constructed so as to develop a positive flow adequate to convey flue or vent gases to the outdoors.
A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer's instructions.
Appliances required to be vented shall be connected to a venting system designed and installed in accordance with the provisions of Sections 503.4 through 503.16.
Mechanical draft systems shall comply with the following:
  1. Mechanical draft systems shall be listed and shall be installed in accordance with the manufacturer's installation instructions for both the appliance and the mechanical draft system.
  2. Appliances, except incinerators, requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design.
  3. Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed so as to prevent leakage of flue or vent gases into a building.
  4. Vent connectors serving appliances vented by natural draft shall not be connected into any portion of mechanical draft systems operating under positive pressure.
  5. Where a mechanical draft system is employed, provisions shall be made to prevent the flow of gas to the main burners when the draft system is not performing so as to satisfy the operating requirements of the appliance for safe performance.
  6. The exit terminals of mechanical draft systems shall be not less than 7 feet (2134 mm) above finished ground level where located adjacent to public walkways and shall be located as specified in Section 503.8, Items 1 and 2.
Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications. Where automatically operated appliances, other than commercial cooking appliances, are vented through a ventilating hood or exhaust system equipped with a damper or with a power means of exhaust, provisions shall be made to allow the flow of gas to the main burners only when the damper is open to a position to properly vent the appliance and when the power means of exhaust is in operation.
Venting systems shall not extend into or pass through any fabricated air duct or furnace plenum.
Where a venting system passes through an above-ceiling air-handling space or other nonducted portion of an air-handling system, the venting system shall conform to one of the following requirements:
  1. The venting system shall be a listed special gas vent; other venting system serving a Category III or Category IV appliance; or other positive pressure vent, with joints sealed in accordance with the appliance or vent manufacturer's instructions.
  2. The venting system shall be installed such that fittings and joints between sections are not installed in the above-ceiling space.
  3. The venting system shall be installed in a conduit or enclosure with sealed joints separating the interior of the conduit or enclosure from the ceiling space.
The type of venting system to be used shall be in accordance with Table 503.4.

TABLE 503.4
TYPE OF VENTING SYSTEM TO BE USED
APPLIANCES TYPE OF VENTING SYSTEM
  Type B gas vent (Section 503.6)   
Listed Category I appliances Chimney (Section 503.5)
Listed appliances equipped with draft hood Single-wall metal pipe (Section 503.7)
Appliances listed for use with Type B gas vent Listed chimney lining system for gas venting (Section 503.5.3)
  Special gas vent listed for these appliances (Section 503.4.2)
Listed vented wall furnaces Type B-W gas vent (Sections 503.6, 608)
Category II appliances As specified or furnished by manufacturers of listed appliances
(Sections 503.4.1, 503.4.2)
Category III appliances As specified or furnished by manufacturers of listed appliances
(Sections 503.4.1, 503.4.2)
Category IV appliances As specified or furnished by manufacturers of listed appliances
(Sections 503.4.1, 503.4.2)
Incinerators, indoors Chimney (Section 503.5)
Incinerators, outdoors Single-wall metal pipe (Sections 503.7, 503.7.6)
Appliances that can be converted for use with solid fuel Chimney (Section 503.5)
Unlisted combination gas and oil-burning appliances Chimney (Section 503.5)
Listed combination gas and oil-burning appliances Type L vent (Section 503.6) or chimney (Section 503.5)
Combination gas and solid fuel-burning appliances Chimney (Section 503.5)
Appliances listed for use with chimneys only Chimney (Section 503.5)
Unlisted appliances Chimney (Section 503.5)
Decorative appliances in vented fireplaces Chimney
Gas-fired toilets Single-wall metal pipe (Section 626)
Direct-vent appliances See Section 503.2.3
Appliances with integral vent See Section 503.2.4
Plastic piping used for venting appliances listed for use with such venting materials shall be approved.
Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer's installation instructions. Where a primer is required, it shall be of a contrasting color.
Special gas vent shall be listed and installed in accordance with the special gas vent manufacturer's installation instructions.
Masonry, metal and factory-built chimneys shall comply with Sections 503.5.1 through 503.5.10.
Factory-built chimneys shall be installed in accordance with the manufacturer's installation instructions. Factory-built chimneys used to vent appliances that operate at a positive vent pressure shall be listed for such application.
Metal chimneys shall be built and installed in accordance with NFPA 211.
Masonry chimneys shall be built and installed in accordance with NFPA 211 and shall be lined with approved clay flue lining, a listed chimney lining system or other approved material that will resist corrosion, erosion, softening or cracking from vent gases at temperatures up to 1,800°F (982°C).
Exception: Masonry chimney flues serving listed gas appliances with draft hoods, Category I appliances and other gas appliances listed for use with Type B vents shall be permitted to be lined with a chimney lining system specifically listed for use only with such appliances. The liner shall be installed in accordance with the liner manufacturer's installation instructions. A permanent identifying label shall be attached at the point where the connection is to be made to the liner. The label shall read: "This chimney liner is for appliances that burn gas only. Do not connect to solid or liquid fuel-burning appliances or incinerators."
For installation of gas vents in existing masonry chimneys, see Section 503.6.3.
Chimneys for residential- type or low-heat appliances shall extend at least 3 feet (914 mm) above the highest point where they pass through a roof of a building and at least 2 feet (610 mm) higher than any portion of a building within a horizontal distance of 10 feet (3048 mm) (see Figure 503.5.4). Chimneys for medium-heat appliances shall extend at least 10 feet (3048 mm) higher than any portion of any building within 25 feet (7620 mm). Chimneys shall extend at least 5 feet (1524 mm) above the highest connected appliance draft hood outlet or flue collar. Decorative shrouds shall not be installed at the termination of factory-built chimneys except where such shrouds are listed and labeled for use with the specific factory-built chimney system and are installed in accordance with the manufacturer's installation instructions.

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FIGURE 503.5.4
TYPICAL TERMINATION LOCATIONS FOR CHIMNEYS AND SINGLE-WALL METAL PIPES SERVING RESIDENTIAL-TYPE AND LOW-HEAT APPLIANCES
The effective area of a chimney venting system serving listed appliances with draft hoods, Category I appliances and other appliances listed for use with Type B vents shall be determined in accordance with one of the following methods:
  1. The provisions of Section 504.
  2. For sizing an individual chimney venting system for a single appliance with a draft hood, the effective areas of the vent connector and chimney flue shall be not less than the area of the appliance flue collar or draft hood outlet, nor greater than seven times the draft hood outlet area.
  3. For sizing a chimney venting system connected to two appliances with draft hoods, the effective area of the chimney flue shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet, nor greater than seven times the smallest draft hood outlet area.
  4. Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods.
  5. Other approved engineering methods.
Before replacing an existing appliance or connecting a vent connector to a chimney, the chimney passageway shall be examined to ascertain that it is clear and free of obstructions and it shall be cleaned if previously used for venting solid or liquid fuel-burning appliances or fireplaces.
Chimneys shall be lined in accordance with NFPA 211.
Exception: Where an existing chimney complies with Sections 503.5.6 through 503.5.6.3 and its sizing is in accordance with Section 503.5.5, its continued use shall be allowed where the appliance vented by such chimney is replaced by an appliance of similar type, input rating and efficiency.
Cleanouts shall be examined to determine if they will remain tightly closed when not in use.
Where inspection reveals that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, relined or replaced with a vent or chimney to conform to NFPA 211 and it shall be suitable for the appliances to be vented.
Chimneys serving appliances burning other fuels shall comply with Sections 503.5.7.1 through 503.5.7.4.
An appliance shall not be connected to a chimney flue serving a separate appliance designed to burn solid fuel.
Where one chimney flue serves gas appliances and liquid fuel-burning appliances, the appliances shall be connected through separate openings or shall be connected through a single opening where joined by a suitable fitting located as close as practical to the chimney. Where two or more openings are provided into one chimney flue, they shall be at different levels. Where the appliances are automatically controlled, they shall be equipped with safety shutoff devices.
A combination gas- and solid fuel-burning appliance shall be permitted to be connected to a single chimney flue where equipped with a manual reset device to shut off gas to the main burner in the event of sustained backdraft or flue gas spillage. The chimney flue shall be sized to properly vent the appliance.
A listed combination gas- and oil fuel-burning appliance shall be permitted to be connected to a single chimney flue. The chimney flue shall be sized to properly vent the appliance.
All portions of chimneys shall be supported for the design and weight of the materials employed. Factory-built chimneys shall be supported and spaced in accordance with the manufacturer's installation instructions.
Where a chimney that formerly carried flue products from liquid or solid fuel-burning appliances is used with an appliance using fuel gas, an accessible cleanout shall be provided. The cleanout shall have a tight-fitting cover and shall be installed so its upper edge is at least 6 inches (152 mm) below the lower edge of the lowest chimney inlet opening.
The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry chimney flue shall not be used to vent another appliance. The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer's instructions shall not be prohibited.
The remaining space surrounding a chimney liner, gas vent, special gas vent or plastic piping installed within a masonry, metal or factory-built chimney shall not be used to supply combustion air. Such space shall not be prohibited from supplying combustion air to direct-vent appliances designed for installation in a solid fuel-burning fireplace and installed in accordance with the manufacturer's installation instructions.
Gas vents shall comply with Sections 503.6.1 through 503.6.13 (see Section 202, Definitions).
Gas vents shall be installed in accordance with the manufacturer's installation instructions.
A Type B-W gas vent shall have a listed capacity not less than that of the listed vented wall furnace to which it is connected.
Gas vents installed within masonry chimneys shall be installed in accordance with the manufacturer's installation instructions. Gas vents installed within masonry chimneys shall be identified with a permanent label installed at the point where the vent enters the chimney. The label shall contain the following language: "This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel-burning appliances or incinerators."
A gas vent shall terminate in accordance with one of the following:
  1. Gas vents that are 12 inches (305 mm) or less in size and located not less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall terminate above the roof in accordance with Figure 503.6.4.
  2. Gas vents that are over 12 inches (305 mm) in size or are located less than 8 feet (2438 mm) from a vertical wall or similar obstruction shall terminate not less than 2 feet (610 mm) above the highest point where they pass through the roof and not less than 2 feet (610 mm) above any portion of a building within 10 feet (3048 mm) horizontally.
  3. As provided for industrial appliances in Section 503.2.2.
  4. As provided for direct-vent systems in Section 503.2.3.
  5. As provided for appliances with integral vents in Section 503.2.4.
  6. As provided for mechanical draft systems in Section 503.3.3.
  7. As provided for ventilating hoods and exhaust systems in Section 503.3.4.
ROOF SLOPE
H (min) ft
Flat to 6/12
1.0
Over 6/12 to 7/12
1.25
Over 7/12 to 8/12
1.5
Over 8/12 to 9/12
2.0
Over 9/12 to 10/12
2.5
Over 10/12 to 11/12
3.25
Over 11/12 to 12/12
4.0
Over 12/12 to 14/12
5.0
Over 14/12 to 16/12
6.0
Over 16/12 to 18/12
7.0
Over 18/12 to 20/12
7.5
Over 20/12 to 21/12
8.0
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FIGURE 503.6.4
TERMINATION LOCATIONS FOR GAS VENTS WITH
LISTED CAPS 12 INCHES OR LESS IN SIZE AT LEAST 8 FEET FROM A VERTICAL WALL
Decorative shrouds shall not be installed at the termination of gas vents except where such shrouds are listed for use with the specific gas venting system and are installed in accordance with manufacturer's installation instructions.
A Type B or L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar. A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
Gas vents shall extend through the roof flashing, roof jack or roof thimble and terminate with a listed cap or listed roof assembly.
Gas vents shall terminate not less than 3 feet (914 mm) above any forced air inlet located within 10 feet (3048 mm).
A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Sections 503.2.3 and 503.3.3.
Venting systems shall be sized and constructed in accordance with Section 504 or other approved engineering methods and the gas vent and appliance manufacturer's installation instructions.
The sizing of natural draft venting systems serving one or more listed appliances equipped with a draft hood or appliances listed for use with Type B gas vent, installed in a single story of a building, shall be in accordance with one of the following methods:
  1. The provisions of Section 504.
  2. For sizing an individual gas vent for a single, draft-hood-equipped appliance, the effective area of the vent connector and the gas vent shall be not less than the area of the appliance draft hood outlet, nor greater than seven times the draft hood outlet area.
  3. For sizing a gas vent connected to two appliances with draft hoods, the effective area of the vent shall be not less than the area of the larger draft hood outlet plus 50 percent of the area of the smaller draft hood outlet, nor greater than seven times the smaller draft hood outlet area.
  4. Approved engineering practices.
Type B and L vents sized in accordance with Item 2 or 3 of Section 503.6.9.1 shall extend in a generally vertical direction with offsets not exceeding 45 degrees (0.79 rad), except that a vent system having not more than one 60-degree (1.04 rad) offset shall be permitted. Any angle greater than 45 degrees (0.79 rad) from the vertical is considered horizontal. The total horizontal distance of a vent plus the horizontal vent connector serving draft hood-equipped appliances shall be not greater than 75 percent of the vertical height of the vent.
The sizing of gas vents for Category II, III and IV appliances shall be in accordance with the appliance manufacturer's instructions.
Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods.
A common gas vent shall be permitted in multistory installations to vent Category I appliances located on more than one floor level, provided that the venting system is designed and installed in accordance with approved engineering methods. For the purpose of this section, crawl spaces, basements and attics shall be considered as floor levels.
All appliances connected to the common vent shall be located in rooms separated from occupiable space. Each of these rooms shall have provisions for an adequate supply of combustion, ventilation and dilution air that is not supplied from an occupiable space (see Figure 503.6.10.1).
FIGURE 503.6.10.1
PLAN VIEW OF PRACTICAL SEPARATION METHOD
FOR MULTISTORY GAS VENTING
The size of the connectors and common segments of multistory venting systems for appliances listed for use with Type B double-wall gas vents shall be in accordance with Table 504.3(1), provided that:
  1. The available total height (H) for each segment of a multistory venting system is the vertical distance between the level of the highest draft hood outlet or flue collar on that floor and the centerline of the next highest interconnection tee (see Figure B-13).
  2. The size of the connector for a segment is determined from the appliance input rating and available connector rise, and shall not be smaller than the draft hood outlet or flue collar size.
  3. The size of the common vertical segment, and of the interconnection tee at the base of that segment, shall be based on the total appliance input rating entering that segment and its available total height.
Gas vents shall be supported and spaced in accordance with the manufacturer's installation instructions.
In those localities where solid and liquid fuels are used extensively, gas vents shall be permanently identified by a label attached to the wall or ceiling at a point where the vent connector enters the gas vent. The determination of where such localities exist shall be made by the code official. The label shall read:
"This gas vent is for appliances that burn gas. Do not connect to solid or liquid fuel-burning appliances or incinerators."
Screws, rivets and other fasteners shall not penetrate the inner wall of double-wall gas vents, except at the transition from an appliance draft hood outlet, a flue collar or a single-wall metal connector to a double-wall vent.
Single-wall metal pipe vents shall comply with Sections 503.7.1 through 503.7.13.
Single-wall metal pipe shall be constructed of galvanized sheet steel not less than 0.0304 inch (0.7 mm) thick, or other approved, noncombustible, corrosion-resistant material.
Uninsulated single-wall metal pipe shall not be used outdoors for venting appliances in regions where the 99-percent winter design temperature is below 32°F (0°C).
Single-wall metal pipe shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood outlet or flue collar. Single-wall metal pipe shall extend at least 2 feet (610 mm) above the highest point where it passes through a roof of a building and at least 2 feet (610 mm) higher than any portion of a building within a horizontal distance of 10 feet (3048 mm) (see Figure 503.5.4). An approved cap or roof assembly shall be attached to the terminus of a single-wall metal pipe (see also Section 503.7.9, Item 3).
Single-wall metal pipe shall be used only for runs directly from the space in which the appliance is located through the roof or exterior wall to the outdoor atmosphere.
A pipe passing through a roof shall extend without interruption through the roof flashing, roof jack or roof thimble. Where a single-wall metal pipe passes through a roof constructed of combustible material, a noncombustible, nonventilating thimble shall be used at the point of passage. The thimble shall extend at least 18 inches (457 mm) above and 6 inches (152 mm) below the roof with the annular space open at the bottom and closed only at the top. The thimble shall be sized in accordance with Section 503.7.7.
Single-wall metal pipe shall not originate in any unoccupied attic or concealed space and shall not pass through any attic, inside wall, concealed space or floor. The installation of a single-wall metal pipe through an exterior combustible wall shall comply with Section 503.7.7. Single-wall metal pipe used for venting an incinerator shall be exposed and readily examinable for its full length and shall have suitable clearances maintained.
A single-wall metal pipe shall not pass through a combustible exterior wall unless guarded at the point of passage by a ventilated metal thimble not smaller than the following:
  1. For listed appliances equipped with draft hoods and appliances listed for use with Type B gas vents, the thimble shall be not less than 4 inches (102 mm) larger in diameter than the metal pipe. Where there is a run of not less than 6 feet (1829 mm) of metal pipe in the open between the draft hood outlet and the thimble, the thimble shall be permitted to be not less than 2 inches (51 mm) larger in diameter than the metal pipe.
  2. For unlisted appliances having draft hoods, the thimble shall be not less than 6 inches (152 mm) larger in diameter than the metal pipe.
  3. For residential and low-heat appliances, the thimble shall be not less than 12 inches (305 mm) larger in diameter than the metal pipe.
Exception: In lieu of thimble protection, all combustible material in the wall shall be removed a sufficient distance from the metal pipe to provide the specified clearance from such metal pipe to combustible material. Any material used to close up such opening shall be noncombustible.
Minimum clearances from single-wall metal pipe to combustible material shall be in accordance with Table 503.10.5. The clearance from single-wall metal pipe to combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 308.2.
A venting system constructed of single-wall metal pipe shall be sized in accordance with one of the following methods and the appliance manufacturer's instructions:
  1. For a draft-hood-equipped appliance, in accordance with Section 504.
  2. For a venting system for a single appliance with a draft hood, the areas of the connector and the pipe each shall be not less than the area of the appliance flue collar or draft hood outlet, whichever is smaller. The vent area shall not be greater than seven times the draft hood outlet area.
  3. Other approved engineering methods.
Any shaped single-wall metal pipe shall be permitted to be used, provided that its equivalent effective area is equal to the effective area of the round pipe for which it is substituted, and provided that the minimum internal dimension of the pipe is not less than 2 inches (51 mm).
The vent cap or a roof assembly shall have a venting capacity not less than that of the pipe to which it is attached.
All portions of single-wall metal pipe shall be supported for the design and weight of the material employed.
Single-wall metal pipe shall comply with the marking provisions of Section 503.6.12.
The location of venting system terminations shall comply with the following (see Appendix C):
  1. A mechanical draft venting system shall terminate at least 3 feet (914 mm) above any forced-air inlet located within 10 feet (3048 mm).
    Exceptions:
    1. This provision shall not apply to the combustion air intake of a direct-vent appliance.
    2. This provision shall not apply to the separation of the integral outdoor air inlet and flue gas discharge of listed outdoor appliances.
  2. A mechanical draft venting system, excluding direct- vent appliances, shall terminate at least 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above any door, operable window or gravity air inlet into any building. The bottom of the vent terminal shall be located at least 12 inches (305 mm) above finished ground level.
  3. The vent terminal of a direct-vent appliance with an input of 10,000 Btu per hour (3 kW) or less shall be located at least 6 inches (152 mm) from any air opening into a building, and such an appliance with an input over 10,000 Btu per hour (3 kW) but not over 50,000 Btu per hour (14.7 kW) shall be installed with a 9-inch (230 mm) vent termination clearance, and an appliance with an input over 50,000 Btu/h (14.7 kW) shall have at least a 12-inch (305 mm) vent termination clearance. The bottom of the vent terminal and the air intake shall be located at least 12 inches (305 mm) above finished ground level.
  4. Through-the-wall vents for Category II and IV appliances and noncategorized condensing appliances shall not terminate over public walkways or over an area where condensate or vapor could create a nuisance or hazard or could be detrimental to the operation of regulators, relief valves or other equipment. Where local experience indicates that condensate is a problem with Category I and III appliances, this provision shall also apply. Drains for condensate shall be installed in accordance with the manufacturer's installation instructions.
Provisions shall be made to collect and dispose of condensate from venting systems serving Category II and IV appliances and noncategorized condensing appliances in accordance with Section 503.8, Item 4. Where local experience indicates that condensation is a problem, provision shall be made to drain off and dispose of condensate from venting systems serving Category I and III appliances in accordance with Section 503.8, Item 4.
A vent connector shall be used to connect an appliance to a gas vent, chimney or single-wall metal pipe, except where the gas vent, chimney or single-wall metal pipe is directly connected to the appliance.
Vent connectors shall be constructed in accordance with Sections 503.10.2.1 through 503.10.2.5.
A vent connector shall be made of noncombustible corrosion-resistant material capable of withstanding the vent gas temperature produced by the appliance and of sufficient thickness to withstand physical damage.
Where the vent connector used for an appliance having a draft hood or a Category I appliance is located in or passes through attics, crawl spaces or other unconditioned spaces, that portion of the vent connector shall be listed Type B, Type L or listed vent material having equivalent insulation properties.
Exception: Single-wall metal pipe located within the exterior walls of the building in areas having a local 99-percent winter design temperature of 5°F (-15°C) or higher shall be permitted to be used in unconditioned spaces other than attics and crawl spaces.
Where vent connectors for residential-type appliances are not installed in attics or other unconditioned spaces, connectors for listed appliances having draft hoods, appliances having draft hoods and equipped with listed conversion burners and Category I appliances shall be one of the following:
  1. Type B or L vent material;
  2. Galvanized sheet steel not less than 0.018 inch (0.46 mm) thick;
  3. Aluminum (1100 or 3003 alloy or equivalent) sheet not less than 0.027 inch (0.69 mm) thick;
  4. Stainless steel sheet not less than 0.012 inch (0.31 mm) thick;
  5. Smooth interior wall metal pipe having resistance to heat and corrosion equal to or greater than that of Item 2, 3 or 4 above; or
  6. A listed vent connector.
Vent connectors shall not be covered with insulation.
Exception: Listed insulated vent connectors shall be installed in accordance with the manufacturer's installation instructions.
A vent connector for a nonresidential, low-heat appliance shall be a factory-built chimney section or steel pipe having resistance to heat and corrosion equivalent to that for the appropriate galvanized pipe as specified in Table 503.10.2.4. Factory-built chimney sections shall be joined together in accordance with the chimney manufacturer's instructions.
 
TABLE 503.10.2.4
MINIMUM THICKNESS FOR GALVANIZED STEEL VENT
CONNECTORS FOR LOW-HEAT APPLIANCES
DIAMETER OF CONNECTOR (inches)
MINIMUM THICKNESS
(inch)
Less than 6
0.019
6 to less than 10
0.023
10 to 12 inclusive
0.029
14 to 16 inclusive
0.034
Over 16
0.056
For SI: 1 inch = 25.4 mm.
Vent connectors for medium-heat appliances and commercial and industrial incinerators shall be constructed of factory-built medium-heat chimney sections or steel of a thickness not less than that specified in Table 503.10.2.5 and shall comply with the following:
  1. A steel vent connector for an appliance with a vent gas temperature in excess of 1,000°F (538°C) measured at the entrance to the connector shall be lined with medium-duty fire brick (ASTM C 64, Type F), or the equivalent.
  2. The lining shall be at least 21/2 inches (64 mm) thick for a vent connector having a diameter or greatest cross-sectional dimension of 18 inches (457 mm) or less.
  3. The lining shall be at least 41/2 inches (114 mm) thick laid on the 41/2-inch (114 mm) bed for a vent connector having a diameter or greatest cross-sectional dimension greater than 18 inches (457 mm).
  4. Factory-built chimney sections, if employed, shall be joined together in accordance with the chimney manufacturer's instructions.
 
TABLE 503.10.2.5
MINIMUM THICKNESS FOR STEEL VENT CONNECTORS FOR
MEDIUM-HEAT APPLIANCES AND COMMERCIAL AND
INDUSTRIAL INCINERATORS VENT CONNECTOR SIZE
DIAMETER
(inches)
AREA
(square inches)
MINIMUM THICKNESS (inch)
Up to 14
Up to 154
0.053
Over 14 to 16
154 to 201
0.067
Over 16 to 18
201 to 254
0.093
Over 18
Larger than 254
0.123
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2.
Vent connectors shall be sized in accordance with Sections 503.10.3.1 through 503.10.3.5.
A vent connector for an appliance with a single draft hood or for a Category I fan-assisted combustion system appliance shall be sized and installed in accordance with Section 504 or other approved engineering methods.
For a single appliance having more than one draft hood outlet or flue collar, the manifold shall be constructed according to the instructions of the appliance manufacturer. Where there are no instructions, the manifold shall be designed and constructed in accordance with approved engineering practices. As an alternate method, the effective area of the manifold shall equal the combined area of the flue collars or draft hood outlets and the vent connectors shall have a minimum 1-foot (305 mm) rise.
Where two or more appliances are connected to a common vent or chimney, each vent connector shall be sized in accordance with Section 504 or other approved engineering methods.
As an alternative method applicable only when all of the appliances are draft hood equipped, each vent connector shall have an effective area not less than the area of the draft hood outlet of the appliance to which it is connected.
Where two or more appliances are vented through a common vent connector or vent manifold, the common vent connector or vent manifold shall be located at the highest level consistent with available headroom and the required clearance to combustible materials and shall be sized in accordance with Section 504 or other approved engineering methods.
As an alternate method applicable only where there are two draft hood-equipped appliances, the effective area of the common vent connector or vent manifold and all junction fittings shall be not less than the area of the larger vent connector plus 50 percent of the area of the smaller flue collar outlet.
Where the size of a vent connector is increased to overcome installation limitations and obtain connector capacity equal to the appliance input, the size increase shall be made at the appliance draft hood outlet.
Where two or more vent connectors enter a common gas vent, chimney flue or single-wall metal pipe, the smaller connector shall enter at the highest level consistent with the available headroom or clearance to combustible material. Vent connectors serving Category I appliances shall not be connected to any portion of a mechanical draft system operating under positive static pressure, such as those serving Category III or IV appliances.
Where two or more openings are provided into one chimney flue or vent, the openings shall be at different levels, or the connectors shall be attached to the vertical portion of the chimney or vent at an angle of 45 degrees (0.79 rad) or less relative to the vertical.
Minimum clearances from vent connectors to combustible material shall be in accordance with Table 503.10.5.
Exception: The clearance between a vent connector and combustible material shall be permitted to be reduced where the combustible material is protected as specified for vent connectors in Table 308.2.
 
TABLE 503.10.5a
CLEARANCES FOR CONNECTORS
MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL
Listed Type B gas
vent material
Listed Type L
vent material
Single-wall
metal pipe
Factory-built
chimney sections
Listed appliances with draft hoods and appliances listed for use with Type B gas vents
As listed
As listed
6 inches
As listed
Residential boilers and furnaces with listed gas conversion burner and with draft hood
6 inches
6 inches
9 inches
As listed
Residential appliances listed for use with Type L vents
Not permitted
As listed
9 inches
As listed
Listed gas-fired toilets
Not permitted
As listed
As listed
As listed
Unlisted residential appliances with draft hood
Not permitted
6 inches
9 inches
As listed
Residential and low-heat appliances other than above
Not permitted
9 inches
18 inches
As listed
Not permitted
Not permitted
36 inches
As listed
For SI: 1 inch = 25.4 mm.
a. These clearances shall apply unless the manufacturer's installation instructions for a listed appliance or connector specify different clearances, in which case the listed clearances shall apply.
A vent connector shall be installed so as to avoid turns or other construction features that create excessive resistance to flow of vent gases.
Joints between sections of connector piping and connections to flue collars and draft hood outlets shall be fastened by one of the following methods:
  1. Sheet metal screws.
  2. Vent connectors of listed vent material assembled and connected to flue collars or draft hood outlets in accordance with the manufacturers' instructions.
  3. Other approved means.
A vent connector shall be installed without dips or sags and shall slope upward toward the vent or chimney at least 1/4 inch per foot (21 mm/m).
Exception: Vent connectors attached to a mechanical draft system installed in accordance with the appliance and draft system manufacturers' instructions.
A vent connector shall be as short as practical and the appliance located as close as practical to the chimney or vent. The maximum horizontal length of a single-wall connector shall be 75 percent of the height of the chimney or vent except for engineered systems. The maximum horizontal length of a Type B double-wall connector shall be 100 percent of the height of the chimney or vent except for engineered systems.
A vent connector shall be supported for the design and weight of the material employed to maintain clearances and prevent physical damage and separation of joints.
Where entering a flue in a masonry or metal chimney, the vent connector shall be installed above the extreme bottom to avoid stoppage. Where a thimble or slip joint is used to facilitate removal of the connector, the connector shall be firmly attached to or inserted into the thimble or slip joint to prevent the connector from falling out. Means shall be employed to prevent the connector from entering so far as to restrict the space between its end and the opposite wall of the chimney flue (see Section 501.9).
The entire length of a vent connector shall be provided with ready access for inspection, cleaning and replacement.
A vent connector shall not be connected to a chimney flue serving a fireplace unless the fireplace flue opening is permanently sealed.
Single-wall metal pipe connectors shall not pass through any wall, floor or ceiling except as permitted by Section 503.7.4.
Vent connectors for medium-heat appliances shall not pass through walls or partitions constructed of combustible material.
Vent connectors for Category II, III and IV appliances shall be as specified for the venting systems in accordance with Section 503.4.
The installation of draft hoods and draft controls shall comply with Sections 503.12.1 through 503.12.7.
Vented appliances shall be installed with draft hoods.
Exception: Dual oven-type combination ranges; incinerators; direct-vent appliances; fan-assisted combustion system appliances; appliances requiring chimney draft for operation; single firebox boilers equipped with conversion burners with inputs greater than 400,000 Btu per hour (117 kW); appliances equipped with blast, power or pressure burners that are not listed for use with draft hoods; and appliances designed for forced venting.
A draft hood supplied with or forming a part of a listed vented appliance shall be installed without alteration, exactly as furnished and specified by the appliance manufacturer.
If a draft hood is not supplied by the appliance manufacturer where one is required, a draft hood shall be installed, shall be of a listed or approved type and, in the absence of other instructions, shall be of the same size as the appliance flue collar. Where a draft hood is required with a conversion burner, it shall be of a listed or approved type.
Where it is determined that a draft hood of special design is needed or preferable for a particular installation, the installation shall be in accordance with the recommendations of the appliance manufacturer and shall be approved.
Where a draft control device is part of the appliance or is supplied by the appliance manufacturer, it shall be installed in accordance with the manufacturer's instructions. In the absence of manufacturer's instructions, the device shall be attached to the flue collar of the appliance or as near to the appliance as practical.
Appliances (except incinerators) requiring a controlled chimney draft shall be permitted to be equipped with a listed double-acting barometric-draft regulator installed and adjusted in accordance with the manufacturer's instructions.
Draft hoods and barometric draft regulators shall be installed in the same room or enclosure as the appliance in such a manner as to prevent any difference in pressure between the hood or regulator and the combustion air supply.
Draft hoods and draft regulators shall be installed in the position for which they were designed with reference to the horizontal and vertical planes and shall be located so that the relief opening is not obstructed by any part of the appliance or adjacent construction. The appliance and its draft hood shall be located so that the relief opening is accessible for checking vent operation.
A draft hood shall be located so its relief opening is not less than 6 inches (152 mm) from any surface except that of the appliance it serves and the venting system to which the draft hood is connected. Where a greater or lesser clearance is indicated on the appliance label, the clearance shall be not less than that specified on the label. Such clearances shall not be reduced.
A manually operated damper shall not be placed in the vent connector for any appliance. Fixed baffles shall not be classified as manually operated dampers.
An automatically operated vent damper shall be of a listed type.
Devices that retard the flow of vent gases shall not be installed in a vent connector, chimney or vent. The following shall not be considered as obstructions:
  1. Draft regulators and safety controls specifically listed for installation in venting systems and installed in accordance with the manufacturer's installation instructions.
  2. Approved draft regulators and safety controls that are designed and installed in accordance with approved engineering methods.
  3. Listed heat reclaimers and automatically operated vent dampers installed in accordance with the manufacturer's installation instructions.
  4. Approved economizers, heat reclaimers and recuperators installed in venting systems of appliances not required to be equipped with draft hoods, provided that the appliance manufacturer's instructions cover the installation of such a device in the venting system and performance in accordance with Sections 503.3 and 503.3.1 is obtained.
  5. Vent dampers serving listed appliances installed in accordance with Sections 504.2.1 and 504.3.1 or other approved engineering methods.
Where vents, including those for direct-vent appliances, penetrate outside walls of buildings, the annular spaces around such penetrations shall be permanently sealed using approved materials to prevent entry of combustion products into the building.
The following definitions apply to the tables in this section.
APPLIANCE CATEGORIZED VENT DIAMETER/ AREA. The minimum vent area/diameter permissible for Category I appliances to maintain a nonpositive vent static pressure when tested in accordance with nationally recognized standards.
FAN-ASSISTED COMBUSTION SYSTEM. An appliance equipped with an integral mechanical means to either draw or force products of combustion through the combustion chamber or heat exchanger.
FAN Min. The minimum input rating of a Category I fan-assisted appliance attached to a vent or connector.
FAN Max. The maximum input rating of a Category I fan-assisted appliance attached to a vent or connector.
NAT Max. The maximum input rating of a Category I draft-hood-equipped appliance attached to a vent or connector.
FAN + FAN. The maximum combined appliance input rating of two or more Category I fan-assisted appliances attached to the common vent.
FAN + NAT. The maximum combined appliance input rating of one or more Category I fan-assisted appliances and one or more Category I draft-hood-equipped appliances attached to the common vent.
NA. Vent configuration is not allowed due to potential for condensate formation or pressurization of the venting system, or not applicable due to physical or geometric restraints.
NAT + NAT. The maximum combined appliance input rating of two or more Category I draft-hood-equipped appliances attached to the common vent.
The application of Tables 504.2(1) through 504.2(6) shall be subject to the requirements of Sections 504.2.1 through 504.2.16.
TABLE 504.2(1)
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Connected directly to vent
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
3
4
5
6
7
8
9
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
0
0
78
46
0
152
86
0
251
141
0
375
205
0
524
285
0
698
370
0
897
470
2
13
51
36
18
97
67
27
157
105
32
232
157
44
321
217
53
425
285
63
543
370
4
21
49
34
30
94
64
39
153
103
50
227
153
66
316
211
79
419
279
93
536
362
6
25
46
32
36
91
61
47
149
100
59
223
149
78
310
205
93
413
273
110
530
354
8
0
0
84
50
0
165
94
0
276
155
0
415
235
0
583
320
0
780
415
0
1,006
537
2
12
57
40
16
109
75
25
178
120
28
263
180
42
365
247
50
483
322
60
619
418
5
23
53
38
32
103
71
42
171
115
53
255
173
70
356
237
83
473
313
99
607
407
8
28
49
35
39
98
66
51
164
109
64
247
165
84
347
227
99
463
303
117
596
396
10
0
0
88
53
0
175
100
0
295
166
0
447
255
0
631
345
0
847
450
0
1,096
585
2
12
61
42
17
118
81
23
194
129
26
289
195
40
402
273
48
533
355
57
684
457
5
23
57
40
32
113
77
41
187
124
52
280
188
68
392
263
81
522
346
95
671
446
10
30
51
36
41
104
70
54
176
115
67
267
175
88
376
245
104
504
330
122
651
427
15
0
0
94
58
0
191
112
0
327
187
0
502
285
0
716
390
0
970
525
0
1,263
682
2
11
69
48
15
136
93
20
226
150
22
339
225
38
475
316
45
633
414
53
815
544
5
22
65
45
30
130
87
39
219
142
49
330
217
64
463
300
76
620
403
90
800
529
10
29
59
41
40
121
82
51
206
135
64
315
208
84
445
288
99
600
386
116
777
507
15
35
53
37
48
112
76
61
195
128
76
301
198
98
429
275
115
580
373
134
755
491
20
0
0
97
61
0
202
119
0
349
202
0
540
307
0
776
430
0
1,057
575
0
1,384
752
2
10
75
51
14
149
100
18
250
166
20
377
249
33
531
346
41
711
470
50
917
612
5
21
71
48
29
143
96
38
242
160
47
367
241
62
519
337
73
697
460
86
902
599
10
28
64
44
38
133
89
50
229
150
62
351
228
81
499
321
95
675
443
112
877
576
15
34
58
40
46
124
84
59
217
142
73
337
217
94
481
308
111
654
427
129
853
557
20
48
52
35
55
116
78
69
206
134
84
322
206
107
464
295
125
634
410
145
830
537
(continued)
TABLE 504.2(1)
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Connected directly to vent
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
3
4
5
6
7
8
9
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
30
0
0
100
64
0
213
128
0
374
220
0
587
336
0
853
475
0
1,173
650
0
1,548
855
2
9
81
56
13
166
112
14
283
185
18
432
280
27
613
394
33
826
535
42
1,072
700
5
21
77
54
28
160
108
36
275
176
45
421
273
58
600
385
69
811
524
82
1,055
688
10
27
70
50
37
150
102
48
262
171
59
405
261
77
580
371
91
788
507
107
1,028
668
15
33
64
NA
44
141
96
57
249
163
70
389
249
90
560
357
105
765
490
124
1,002
648
20
56
58
NA
53
132
90
66
237
154
80
374
237
102
542
343
119
743
473
139
977
628
30
NA
NA
NA
73
113
NA
88
214
NA
104
346
219
131
507
321
149
702
444
171
929
594
50
0
0
101
67
0
216
134
0
397
232
0
633
363
0
932
518
0
1,297
708
0
1,730
952
2
8
86
61
11
183
122
14
320
206
15
497
314
22
715
445
26
975
615
33
1,276
813
5
20
82
NA
27
177
119
35
312
200
43
487
308
55
702
438
65
960
605
77
1,259
798
10
26
76
NA
35
168
114
45
299
190
56
471
298
73
681
426
86
935
589
101
1,230
773
15
59
70
NA
42
158
NA
54
287
180
66
455
288
85
662
413
100
911
572
117
1,203
747
20
NA
NA
NA
50
149
NA
63
275
169
76
440
278
97
642
401
113
888
556
131
1,176
722
30
NA
NA
NA
69
131
NA
84
250
NA
99
410
259
123
605
376
141
844
522
161
1,125
670
100
0
NA
NA
NA
0
218
NA
0
407
NA
0
665
400
0
997
560
0
1,411
770
0
1,908
1,040
2
NA
NA
NA
10
194
NA
12
354
NA
13
566
375
18
831
510
21
1,155
700
25
1,536
935
5
NA
NA
NA
26
189
NA
33
347
NA
40
557
369
52
820
504
60
1,141
692
71
1,519
926
10
NA
NA
NA
33
182
NA
43
335
NA
53
542
361
68
801
493
80
1,118
679
94
1,492
910
15
NA
NA
NA
40
174
NA
50
321
NA
62
528
353
80
782
482
93
1,095
666
109
1,465
895
20
NA
NA
NA
47
166
NA
59
311
NA
71
513
344
90
763
471
105
1,073
653
122
1,438
880
30
NA
NA
NA
NA
NA
NA
78
290
NA
92
483
NA
115
726
449
131
1,029
627
149
1,387
849
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
147
428
NA
180
651
405
197
944
575
217
1,288
787
(continued)
TABLE 504.2(1)—continued
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Connected directly to vent
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
10
12
14
16
18
20
22
24
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
0
0
1,121
570
0
1,645
850
0
2,267
1,170
0
2,983
1,530
0
3,802
1,960
0
4,721
2,430
0
5,737
2,950
0
6,853
3,520
2
75
675
455
103
982
650
138
1,346
890
178
1,769
1,170
225
2,250
1,480
296
2,782
1,850
360
3,377
2,220
426
4,030
2,670
4
110
668
445
147
975
640
191
1,338
880
242
1,761
1,160
300
2,242
1,475
390
2,774
1,835
469
3,370
2,215
555
4,023
2,660
6
128
661
435
171
967
630
219
1,330
870
276
1,753
1,150
341
2,235
1,470
437
2,767
1,820
523
3,363
2,210
618
4,017
2,650
8
0
0
1,261
660
0
1,858
970
0
2,571
1,320
0
3,399
1,740
0
4,333
2,220
0
5,387
2,750
0
6,555
3,360
0
7,838
4,010
2
71
770
515
98
1,124
745
130
1,543
1,020
168
2,030
1,340
212
2,584
1,700
278
3,196
2,110
336
3,882
2,560
401
4,634
3,050
5
115
758
503
154
1,110
733
199
1,528
1,010
251
2,013
1,330
311
2,563
1,685
398
3,180
2,090
476
3,863
2,545
562
4,612
3,040
8
137
746
490
180
1,097
720
231
1,514
1,000
289
2,000
1,320
354
2,552
1,670
450
3,163
2,070
537
3,850
2,530
630
4,602
3,030
10
0
0
1,377
720
0
2,036
1,060
0
2,825
1,450
0
3,742
1,925
0
4,782
2,450
0
5,955
3,050
0
7,254
3,710
0
8,682
4,450
2
68
852
560
93
1,244
850
124
1,713
1,130
161
2,256
1,480
202
2,868
1,890
264
3,556
2,340
319
4,322
2,840
378
5,153
3,390
5
112
839
547
149
1,229
829
192
1,696
1,105
243
2,238
1,461
300
2,849
1,871
382
3,536
2,318
458
4,301
2,818
540
5,132
3,371
10
142
817
525
187
1,204
795
238
1,669
1,080
298
2,209
1,430
364
2,818
1,840
459
3,504
2,280
546
4,268
2,780
641
5,099
3,340
15
0
0
1,596
840
0
2,380
1,240
0
3,323
1,720
0
4,423
2,270
0
5,678
2,900
0
7,099
3,620
0
8,665
4,410
0
10,393
5,300
2
63
1,019
675
86
1,495
985
114
2,062
1,350
147
2,719
1,770
186
3,467
2,260
239
4,304
2,800
290
5,232
3,410
346
6,251
4,080
5
105
1,003
660
140
1,476
967
182
2,041
1,327
229
2,696
1,748
283
3,442
2,235
355
4,278
2,777
426
5,204
3,385
501
6,222
4,057
10
135
977
635
177
1,446
936
227
2,009
1,289
283
2,659
1,712
346
3,402
2,193
432
4,234
2,739
510
5,159
3,343
599
6,175
4,019
15
155
953
610
202
1,418
905
257
1,976
1,250
318
2,623
1,675
385
3,363
2,150
479
4,192
2,700
564
5,115
3,300
665
6,129
3,980
20
0
0
1,756
930
0
2,637
1,350
0
3,701
1,900
0
4,948
2,520
0
6,376
3,250
0
7,988
4,060
0
9,785
4,980
0
11,753
6,000
2
59
1,150
755
81
1,694
1,100
107
2,343
1,520
139
3,097
2,000
175
3,955
2,570
220
4,916
3,200
269
5,983
3,910
321
7,154
4,700
5
101
1,133
738
135
1,674
1,079
174
2,320
1,498
219
3,071
1,978
270
3,926
2,544
337
4,885
3,174
403
5,950
3,880
475
7,119
4,662
10
130
1,105
710
172
1,641
1,045
220
2,282
1,460
273
3,029
1,940
334
3,880
2,500
413
4,835
3,130
489
5,896
3,830
573
7,063
4,600
15
150
1,078
688
195
1,609
1,018
248
2,245
1,425
306
2,988
1,910
372
3,835
2,465
459
4,786
3,090
541
5,844
3,795
631
7,007
4,575
20
167
1,052
665
217
1,578
990
273
2,210
1,390
335
2,948
1,880
404
3,791
2,430
495
4,737
3,050
585
5,792
3,760
689
6,953
4,550
(continued)
TABLE 504.2(1)—continued
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Connected directly to vent
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
10
12
14
16
18
20
22
24
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
30
0
0
1,977
1,060
0
3,004
1,550
0
4,252
2,170
0
5,725
2,920
0
7,420
3,770
0
9,341
4,750
0
11,483
5,850
0
13,848
7,060
2
54
1,351
865
74
2,004
1,310
98
2,786
1,800
127
3,696
2,380
159
4,734
3,050
199
5,900
3,810
241
7,194
4,650
285
8,617
5,600
5
96
1,332
851
127
1,981
1,289
164
2,759
1,775
206
3,666
2,350
252
4,701
3,020
312
5,863
3,783
373
7,155
4,622
439
8,574
5,552
10
125
1,301
829
164
1,944
1,254
209
2,716
1,733
259
3,617
2,300
316
4,647
2,970
386
5,803
3,739
456
7,090
4,574
535
8,505
5,471
15
143
1,272
807
187
1,908
1,220
237
2,674
1,692
292
3,570
2,250
354
4,594
2,920
431
5,744
3,695
507
7,026
4,527
590
8,437
5,391
20
160
1,243
784
207
1,873
1,185
260
2,633
1,650
319
3,523
2,200
384
4,542
2,870
467
5,686
3,650
548
6,964
4,480
639
8,370
5,310
30
195
1,189
745
246
1,807
1,130
305
2,555
1,585
369
3,433
2,130
440
4,442
2,785
540
5,574
3,565
635
6,842
4,375
739
8,239
5,225
50
0
0
2,231
1,195
0
3,441
1,825
0
4,934
2,550
0
6,711
3,440
0
8,774
4,460
0
11,129
5,635
0
13,767
6,940
0
16,694
8,430
2
41
1,620
1,010
66
2,431
1,513
86
3,409
2,125
113
4,554
2,840
141
5,864
3,670
171
7,339
4,630
209
8,980
5,695
251
10,788
6,860
5
90
1,600
996
118
2,406
1,495
151
3,380
2,102
191
4,520
2,813
234
5,826
3,639
283
7,295
4,597
336
8,933
5,654
394
10,737
6,818
10
118
1,567
972
154
2,366
1,466
196
3,332
2,064
243
4,464
2,767
295
5,763
3,585
355
7,224
4,542
419
8,855
5,585
491
10,652
6,749
15
136
1,536
948
177
2,327
1,437
222
3,285
2,026
274
4,409
2,721
330
5,701
3,534
396
7,155
4,511
465
8,779
5,546
542
10,570
6,710
20
151
1,505
924
195
2,288
1,408
244
3,239
1,987
300
4,356
2,675
361
5,641
3,481
433
7,086
4,479
506
8,704
5,506
586
10,488
6,670
30
183
1,446
876
232
2,214
1,349
287
3,150
1,910
347
4,253
2,631
412
5,523
3,431
494
6,953
4,421
577
8,557
5,444
672
10,328
6,603
100
0
0
2,491
1,310
0
3,925
2,050
0
5,729
2,950
0
7,914
4,050
0
10,485
5,300
0
13,454
6,700
0
16,817
8,600
0
20,578
10,300
2
30
1,975
1,170
44
3,027
1,820
72
4,313
2,550
95
5,834
3,500
120
7,591
4,600
138
9,577
5,800
169
11,803
7,200
204
14,264
8,800
5
82
1,955
1,159
107
3,002
1,803
136
4,282
2,531
172
5,797
3,475
208
7,548
4,566
245
9,528
5,769
293
11,748
7,162
341
14,204
8,756
10
108
1,923
1,142
142
2,961
1,775
180
4,231
2,500
223
5,737
3,434
268
7,478
4,509
318
9,447
5,717
374
11,658
7,100
436
14,105
8,683
15
126
1,892
1,124
163
2,920
1,747
206
4,182
2,469
252
5,678
3,392
304
7,409
4,451
358
9,367
5,665
418
11,569
7,037
487
14,007
8,610
20
141
1,861
1,107
181
2,880
1,719
226
4,133
2,438
277
5,619
3,351
330
7,341
4,394
387
9,289
5,613
452
11,482
6,975
523
13,910
8,537
30
170
1,802
1,071
215
2,803
1,663
265
4,037
2,375
319
5,505
3,267
378
7,209
4,279
446
9,136
5,509
514
11,310
6,850
592
13,720
8,391
50
241
1,688
1,000
292
2,657
1,550
350
3,856
2,250
415
5,289
3,100
486
6,956
4,050
572
8,841
5,300
659
10,979
6,600
752
13,354
8,100
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.2(2)
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Single-wall metal connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
0
38
77
45
59
151
85
85
249
140
126
373
204
165
522
284
211
695
369
267
894
469
371
1,118
569
537
1,639
849
2
39
51
36
60
96
66
85
156
104
123
231
156
159
320
213
201
423
284
251
541
368
347
673
453
498
979
648
4
NA
NA
33
74
92
63
102
152
102
146
225
152
187
313
208
237
416
277
295
533
360
409
664
443
584
971
638
6
NA
NA
31
83
89
60
114
147
99
163
220
148
207
307
203
263
409
271
327
526
352
449
656
433
638
962
627
8
0
37
83
50
58
164
93
83
273
154
123
412
234
161
580
319
206
777
414
258
1,002
536
360
1,257
658
521
1,852
967
2
39
56
39
59
108
75
83
176
119
121
261
179
155
363
246
197
482
321
246
617
417
339
768
513
486
1,120
743
5
NA
NA
37
77
102
69
107
168
114
151
252
171
193
352
235
245
470
311
305
604
404
418
754
500
598
1,104
730
8
NA
NA
33
90
95
64
122
161
107
175
243
163
223
342
225
280
458
300
344
591
392
470
740
486
665
1,089
715
10
0
37
87
53
57
174
99
82
293
165
120
444
254
158
628
344
202
844
449
253
1,093
584
351
1,373
718
507
2,031
1,057
2
39
61
41
59
117
80
82
193
128
119
287
194
153
400
272
193
531
354
242
681
456
332
849
559
475
1,242
848
5
52
56
39
76
111
76
105
185
122
148
277
186
190
388
261
241
518
344
299
667
443
409
834
544
584
1,224
825
10
NA
NA
34
97
100
68
132
171
112
188
261
171
237
369
241
296
497
325
363
643
423
492
808
520
688
1,194
788
15
0
36
93
57
56
190
111
80
325
186
116
499
283
153
713
388
195
966
523
244
1,259
681
336
1,591
838
488
2,374
1,237
2
38
69
47
57
136
93
80
225
149
115
337
224
148
473
314
187
631
413
232
812
543
319
1,015
673
457
1,491
983
5
51
63
44
75
128
86
102
216
140
144
326
217
182
459
298
231
616
400
287
795
526
392
997
657
562
1,469
963
10
NA
NA
39
95
116
79
128
201
131
182
308
203
228
438
284
284
592
381
349
768
501
470
966
628
664
1,433
928
15
NA
NA
NA
NA
NA
72
158
186
124
220
290
192
272
418
269
334
568
367
404
742
484
540
937
601
750
1,399
894
20
0
35
96
60
54
200
118
78
346
201
114
537
306
149
772
428
190
1,053
573
238
1,379
750
326
1,751
927
473
2,631
1,346
2
37
74
50
56
148
99
78
248
165
113
375
248
144
528
344
182
708
468
227
914
611
309
1,146
754
443
1,689
1,098
5
50
68
47
73
140
94
100
239
158
141
363
239
178
514
334
224
692
457
279
896
596
381
1,126
734
547
1,665
1,074
10
NA
NA
41
93
129
86
125
223
146
177
344
224
222
491
316
277
666
437
339
866
570
457
1,092
702
646
1,626
1,037
15
NA
NA
NA
NA
NA
80
155
208
136
216
325
210
264
469
301
325
640
419
393
838
549
526
1,060
677
730
1,587
1,005
20
NA
NA
NA
NA
NA
NA
186
192
126
254
306
196
309
448
285
374
616
400
448
810
526
592
1,028
651
808
1,550
973
(continued)
TABLE 504.2(2)
TYPE B DOUBLE-WALL GAS VENT
Number of Appliances
Single
Appliance Vent Connection
Single-wall metal connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
30
0
34
99
63
53
211
127
76
372
219
110
584
334
144
849
472
184
1,168
647
229
1,542
852
312
1,971
1,056
454
2,996
1,545
2
37
80
56
55
164
111
76
281
183
109
429
279
139
610
392
175
823
533
219
1,069
698
296
1,346
863
424
1,999
1,308
5
49
74
52
72
157
106
98
271
173
136
417
271
171
595
382
215
806
521
269
1,049
684
366
1,324
846
524
1,971
1,283
10
NA
NA
NA
91
144
98
122
255
168
171
397
257
213
570
367
265
777
501
327
1,017
662
440
1,287
821
620
1,927
1,234
15
NA
NA
NA
115
131
NA
151
239
157
208
377
242
255
547
349
312
750
481
379
985
638
507
1,251
794
702
1,884
1,205
20
NA
NA
NA
NA
NA
NA
181
223
NA
246
357
228
298
524
333
360
723
461
433
955
615
570
1,216
768
780
1,841
1,166
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
389
477
305
461
670
426
541
895
574
704
1,147
720
937
1,759
1,101
50
0
33
99
66
51
213
133
73
394
230
105
629
361
138
928
515
176
1,292
704
220
1,724
948
295
2,223
1,189
428
3,432
1,818
2
36
84
61
53
181
121
73
318
205
104
495
312
133
712
443
168
971
613
209
1,273
811
280
1,615
1,007
401
2,426
1,509
5
48
80
NA
70
174
117
94
308
198
131
482
305
164
696
435
204
953
602
257
1,252
795
347
1,591
991
496
2,396
1,490
10
NA
NA
NA
89
160
NA
118
292
186
162
461
292
203
671
420
253
923
583
313
1,217
765
418
1,551
963
589
2,347
1,455
15
NA
NA
NA
112
148
NA
145
275
174
199
441
280
244
646
405
299
894
562
363
1,183
736
481
1,512
934
668
2,299
1,421
20
NA
NA
NA
NA
NA
NA
176
257
NA
236
420
267
285
622
389
345
866
543
415
1,150
708
544
1,473
906
741
2,251
1,387
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
315
376
NA
373
573
NA
442
809
502
521
1,086
649
674
1,399
848
892
2,159
1,318
100
0
NA
NA
NA
49
214
NA
69
403
NA
100
659
395
131
991
555
166
1,404
765
207
1,900
1,033
273
2,479
1,300
395
3,912
2,042
2
NA
NA
NA
51
192
NA
70
351
NA
98
563
373
125
828
508
158
1,152
698
196
1,532
933
259
1,970
1,168
371
3,021
1,817
5
NA
NA
NA
67
186
NA
90
342
NA
125
551
366
156
813
501
194
1,134
688
240
1,511
921
322
1,945
1,153
460
2,990
1,796
10
NA
NA
NA
85
175
NA
113
324
NA
153
532
354
191
789
486
238
1,104
672
293
1,477
902
389
1,905
1,133
547
2,938
1,763
15
NA
NA
NA
132
162
NA
138
310
NA
188
511
343
230
764
473
281
1,075
656
342
1,443
884
447
1,865
1,110
618
2,888
1,730
20
NA
NA
NA
NA
NA
NA
168
295
NA
224
487
NA
270
739
458
325
1,046
639
391
1,410
864
507
1,825
1,087
690
2,838
1,696
30
NA
NA
NA
NA
NA
NA
231
264
NA
301
448
NA
355
685
NA
418
988
NA
491
1,343
824
631
1,747
1,041
834
2,739
1,627
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
540
584
NA
617
866
NA
711
1,205
NA
895
1,591
NA
1,138
2,547
1,489
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE TABLE 504.2(3)
MASONRY CHIMNEY
Number of Appliances
Single
Appliance Vent Connection
Type B double-wall connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
2
NA
NA
28
NA
NA
52
NA
NA
86
NA
NA
130
NA
NA
180
NA
NA
247
NA
NA
320
NA
NA
401
NA
NA
581
5
NA
NA
25
NA
NA
49
NA
NA
82
NA
NA
117
NA
NA
165
NA
NA
231
NA
NA
298
NA
NA
376
NA
NA
561
8
2
NA
NA
29
NA
NA
55
NA
NA
93
NA
NA
145
NA
NA
198
NA
NA
266
84
590
350
100
728
446
139
1,024
651
5
NA
NA
26
NA
NA
52
NA
NA
88
NA
NA
134
NA
NA
183
NA
NA
247
NA
NA
328
149
711
423
201
1,007
640
8
NA
NA
24
NA
NA
48
NA
NA
83
NA
NA
127
NA
NA
175
NA
NA
239
NA
NA
318
173
695
410
231
990
623
10
2
NA
NA
31
NA
NA
61
NA
NA
103
NA
NA
162
NA
NA
221
68
519
298
82
655
388
98
810
491
136
1,144
724
5
NA
NA
28
NA
NA
57
NA
NA
96
NA
NA
148
NA
NA
204
NA
NA
277
124
638
365
146
791
466
196
1,124
712
10
NA
NA
25
NA
NA
50
NA
NA
87
NA
NA
139
NA
NA
191
NA
NA
263
155
610
347
182
762
444
240
1,093
668
15
2
NA
NA
35
NA
NA
67
NA
NA
114
NA
NA
179
53
475
250
64
613
336
77
779
441
92
968
562
127
1,376
841
5
NA
NA
35
NA
NA
62
NA
NA
107
NA
NA
164
NA
NA
231
99
594
313
118
759
416
139
946
533
186
1,352
828
10
NA
NA
28
NA
NA
55
NA
NA
97
NA
NA
153
NA
NA
216
126
565
296
148
727
394
173
912
567
229
1,315
777
15
NA
NA
NA
NA
NA
48
NA
NA
89
NA
NA
141
NA
NA
201
NA
NA
281
171
698
375
198
880
485
259
1,280
742
20
2
NA
NA
38
NA
NA
74
NA
NA
124
NA
NA
201
51
522
274
61
678
375
73
867
491
87
1,083
627
121
1,548
953
5
NA
NA
36
NA
NA
68
NA
NA
116
NA
NA
184
80
503
254
95
658
350
113
845
463
133
1,059
597
179
1,523
933
10
NA
NA
NA
NA
NA
60
NA
NA
107
NA
NA
172
NA
NA
237
122
627
332
143
811
440
167
1,022
566
221
1,482
879
15
NA
NA
NA
NA
NA
NA
NA
NA
97
NA
NA
159
NA
NA
220
NA
NA
314
165
780
418
191
987
541
251
1,443
840
20
NA
NA
NA
NA
NA
NA
NA
NA
83
NA
NA
148
NA
NA
206
NA
NA
296
186
750
397
214
955
513
277
1,406
807
(continued)
TABLE 504.2(3)—continued
MASONRY CHIMNEY
Number of Appliances
Single
Appliance Vent Connection
Type B double-wall connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
TYPE B DOUBLE-WALL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
30
2
NA
NA
41
NA
NA
82
NA
NA
137
NA
NA
216
47
581
303
57
762
421
68
985
558
81
1,240
717
111
1,793
1,112
5
NA
NA
NA
NA
NA
76
NA
NA
128
NA
NA
198
75
561
281
90
741
393
106
962
526
125
1,216
683
169
1,766
1,094
10
NA
NA
NA
NA
NA
67
NA
NA
115
NA
NA
184
NA
NA
263
115
709
373
135
927
500
158
1,176
648
210
1,721
1,025
15
NA
NA
NA
NA
NA
NA
NA
NA
107
NA
NA
171
NA
NA
243
NA
NA
353
156
893
476
181
1,139
621
239
1,679
981
20
NA
NA
NA
NA
NA
NA
NA
NA
91
NA
NA
159
NA
NA
227
NA
NA
332
176
860
450
203
1,103
592
264
1,638
940
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
188
NA
NA
288
NA
NA
416
249
1,035
555
318
1,560
877
50
2
NA
NA
NA
NA
NA
92
NA
NA
161
NA
NA
251
NA
NA
351
51
840
477
61
1,106
633
72
1,413
812
99
2,080
1,243
5
NA
NA
NA
NA
NA
NA
NA
NA
151
NA
NA
230
NA
NA
323
83
819
445
98
1,083
596
116
1,387
774
155
2,052
1,225
10
NA
NA
NA
NA
NA
NA
NA
NA
138
NA
NA
215
NA
NA
304
NA
NA
424
126
1,047
567
147
1,347
733
195
2,006
1,147
15
NA
NA
NA
NA
NA
NA
NA
NA
127
NA
NA
199
NA
NA
282
NA
NA
400
146
1,010
539
170
1,307
702
222
1,961
1,099
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
185
NA
NA
264
NA
NA
376
165
977
511
190
1,269
669
246
1,916
1,050
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
327
NA
NA
468
233
1,196
623
295
1,832
984
Minimum Internal Area of Chimney (square inches)
12
19
28
38
50
63
78
95
132
Maximum Internal Area of Chimney (square inches)
Seven times the listed appliance categorized vent area, flue collar area or draft hood outlet area.
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.2(4)
MASONRY CHIMNEY
Number of Appliances
Single
Appliance Vent Connection
Single-wall metal connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
SINGLE-WALL METAL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
2
NA
NA
28
NA
NA
52
NA
NA
86
NA
NA
130
NA
NA
180
NA
NA
247
NA
NA
319
NA
NA
400
NA
NA
580
5
NA
NA
25
NA
NA
48
NA
NA
81
NA
NA
116
NA
NA
164
NA
NA
230
NA
NA
297
NA
NA
375
NA
NA
560
8
2
NA
NA
29
NA
NA
55
NA
NA
93
NA
NA
145
NA
NA
197
NA
NA
265
NA
NA
349
382
725
445
549
1,021
650
5
NA
NA
26
NA
NA
51
NA
NA
87
NA
NA
133
NA
NA
182
NA
NA
246
NA
NA
327
NA
NA
422
673
1,003
638
8
NA
NA
23
NA
NA
47
NA
NA
82
NA
NA
126
NA
NA
174
NA
NA
237
NA
NA
317
NA
NA
408
747
985
621
10
2
NA
NA
31
NA
NA
61
NA
NA
102
NA
NA
161
NA
NA
220
216
518
297
271
654
387
373
808
490
536
1,142
722
5
NA
NA
28
NA
NA
56
NA
NA
95
NA
NA
147
NA
NA
203
NA
NA
276
334
635
364
459
789
465
657
1,121
710
10
NA
NA
24
NA
NA
49
NA
NA
86
NA
NA
137
NA
NA
189
NA
NA
261
NA
NA
345
547
758
441
771
1,088
665
15
2
NA
NA
35
NA
NA
67
NA
NA
113
NA
NA
178
166
473
249
211
611
335
264
776
440
362
965
560
520
1,373
840
5
NA
NA
32
NA
NA
61
NA
NA
106
NA
NA
163
NA
NA
230
261
591
312
325
775
414
444
942
531
637
1,348
825
10
NA
NA
27
NA
NA
54
NA
NA
96
NA
NA
151
NA
NA
214
NA
NA
294
392
722
392
531
907
504
749
1,309
774
15
NA
NA
NA
NA
NA
46
NA
NA
87
NA
NA
138
NA
NA
198
NA
NA
278
452
692
372
606
873
481
841
1,272
738
20
2
NA
NA
38
NA
NA
73
NA
NA
123
NA
NA
200
163
520
273
206
675
374
258
864
490
252
1,079
625
508
1,544
950
5
NA
NA
35
NA
NA
67
NA
NA
115
NA
NA
183
80
NA
252
255
655
348
317
842
461
433
1,055
594
623
1,518
930
10
NA
NA
NA
NA
NA
59
NA
NA
105
NA
NA
170
NA
NA
235
312
622
330
382
806
437
517
1,016
562
733
1,475
875
15
NA
NA
NA
NA
NA
NA
NA
NA
95
NA
NA
156
NA
NA
217
NA
NA
311
442
773
414
591
979
539
823
1,434
835
20
NA
NA
NA
NA
NA
NA
NA
NA
80
NA
NA
144
NA
NA
202
NA
NA
292
NA
NA
392
663
944
510
911
1,394
800
TABLE 504.2(4)—continued
MASONRY CHIMNEY
Number of Appliances
Single
Appliance Vent Connection
Single-wall metal connector
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
SINGLE-WALL METAL CONNECTOR DIAMETER—(D) inches
to be used with chimney areas within the size limits at bottom
3
4
5
6
7
8
9
10
12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
30
2
NA
NA
41
NA
NA
81
NA
NA
136
NA
NA
215
158
578
302
200
759
420
249
982
556
340
1,237
715
489
1,789
1,110
5
NA
NA
NA
NA
NA
75
NA
NA
127
NA
NA
196
NA
NA
279
245
737
391
306
958
524
417
1,210
680
600
1,760
1,090
10
NA
NA
NA
NA
NA
66
NA
NA
113
NA
NA
182
NA
NA
260
300
703
370
370
920
496
500
1,168
644
708
1,713
1,020
15
NA
NA
NA
NA
NA
NA
NA
NA
105
NA
NA
168
NA
NA
240
NA
NA
349
428
884
471
572
1,128
615
798
1,668
975
20
NA
NA
NA
NA
NA
NA
NA
NA
88
NA
NA
155
NA
NA
223
NA
NA
327
NA
NA
445
643
1,089
585
883
1,624
932
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
182
NA
NA
281
NA
NA
408
NA
NA
544
1,055
1,539
865
50
2
NA
NA
NA
NA
NA
91
NA
NA
160
NA
NA
250
NA
NA
350
191
837
475
238
1,103
631
323
1,408
810
463
2,076
1,240
5
NA
NA
NA
NA
NA
NA
NA
NA
149
NA
NA
228
NA
NA
321
NA
NA
442
293
1,078
593
398
1,381
770
571
2,044
1,220
10
NA
NA
NA
NA
NA
NA
NA
NA
136
NA
NA
212
NA
NA
301
NA
NA
420
355
1,038
562
447
1,337
728
674
1,994
1,140
15
NA
NA
NA
NA
NA
NA
NA
NA
124
NA
NA
195
NA
NA
278
NA
NA
395
NA
NA
533
546
1,294
695
761
1,945
1,090
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
180
NA
NA
258
NA
NA
370
NA
NA
504
616
1,251
660
844
1,898
1,040
30
NA
NA
NA
NA
NA
48
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
318
NA
NA
458
NA
NA
610
1,009
1,805
970
Minimum Internal Area of Chimney (square inches)
12
19
28
38
50
63
78
95
132
Maximum Internal Area of Chimney (square inches)
Seven times the listed appliance categorized vent area, flue collar area or draft hood outlet area.
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.2(5)
SINGLE-WALL METAL PIPE OR TYPE B
ASBESTOS CEMENT VENT
Number of Appliances
Single
Draft hood equipped
Appliance Vent Connection
Connected directly to pipe or vent
HEIGHT
(H)
(feet)
LATERAL
(L)
(feet)
VENT DIAMETER—(D) inches
3
4
5
6
7
8
10
12
MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
0
39
70
116
170
232
312
500
750
2
31
55
94
141
194
260
415
620
5
28
51
88
128
177
242
390
600
8
0
42
76
126
185
252
340
542
815
2
32
61
102
154
210
284
451
680
5
29
56
95
141
194
264
430
648
10
24
49
86
131
180
250
406
625
10
0
45
84
138
202
279
372
606
912
2
35
67
111
168
233
311
505
760
5
32
61
104
153
215
289
480
724
10
27
54
94
143
200
274
455
700
15
NA
46
84
130
186
258
432
666
15
0
49
91
151
223
312
420
684
1,040
2
39
72
122
186
260
350
570
865
5
35
67
110
170
240
325
540
825
10
30
58
103
158
223
308
514
795
15
NA
50
93
144
207
291
488
760
20
NA
NA
82
132
195
273
466
726
20
0
53
101
163
252
342
470
770
1,190
2
42
80
136
210
286
392
641
990
5
38
74
123
192
264
364
610
945
10
32
65
115
178
246
345
571
910
15
NA
55
104
163
228
326
550
870
20
NA
NA
91
149
214
306
525
832
30
0
56
108
183
276
384
529
878
1,370
2
44
84
148
230
320
441
730
1,140
5
NA
78
137
210
296
410
694
1,080
10
NA
68
125
196
274
388
656
1,050
15
NA
NA
113
177
258
366
625
1,000
20
NA
NA
99
163
240
344
596
960
30
NA
NA
NA
NA
192
295
540
890
50
0
NA
120
210
310
443
590
980
1,550
2
NA
95
171
260
370
492
820
1,290
5
NA
NA
159
234
342
474
780
1,230
10
NA
NA
146
221
318
456
730
1,190
15
NA
NA
NA
200
292
407
705
1,130
20
NA
NA
NA
185
276
384
670
1,080
30
NA
NA
NA
NA
222
330
605
1,010
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.2(6)
EXTERIOR MASONRY CHIMNEY
Number of Appliances
Single
NAT
Appliance Vent Connection
Type B double-wall connector
MINIMUM ALLOWABLE INPUT RATING OF SPACE-HEATING APPLIANCE
IN THOUSANDS OF BTU PER HOUR
VENT HEIGHT
(feet)
Internal area of chimney (square inches)
12
19
28
38
50
63
78
113
37°F or Greater
Local 99% Winter Design Temperature: 37°F or Greater
6
0
0
0
0
0
0
0
0
8
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
15
NA
0
0
0
0
0
0
0
20
NA
NA
123
190
249
184
0
0
30
NA
NA
NA
NA
NA
393
334
0
50
NA
NA
NA
NA
NA
NA
NA
579
27 to 36°F
Local 99% Winter Design Temperature: 27 to 36°F
6
0
0
68
116
156
180
212
266
8
0
0
82
127
167
187
214
263
10
0
51
97
141
183
201
225
265
15
NA
NA
NA
NA
233
253
274
305
20
NA
NA
NA
NA
NA
307
330
362
30
NA
NA
NA
NA
NA
419
445
485
50
NA
NA
NA
NA
NA
NA
NA
763
17 to 26°F
Local 99% Winter Design Temperature: 17 to 26°F
6
NA
NA
NA
NA
NA
215
259
349
8
NA
NA
NA
NA
197
226
264
352
10
NA
NA
NA
NA
214
245
278
358
15
NA
NA
NA
NA
NA
296
331
398
20
NA
NA
NA
NA
NA
352
387
457
30
NA
NA
NA
NA
NA
NA
507
581
50
NA
NA
NA
NA
NA
NA
NA
NA
5 to 16°F
Local 99% Winter Design Temperature: 5 to 16°F
6
NA
NA
NA
NA
NA
NA
NA
416
8
NA
NA
NA
NA
NA
NA
312
423
10
NA
NA
NA
NA
NA
289
331
430
15
NA
NA
NA
NA
NA
NA
393
485
20
NA
NA
NA
NA
NA
NA
450
547
30
NA
NA
NA
NA
NA
NA
NA
682
50
NA
NA
NA
NA
NA
NA
NA
972
-10 to 4°F
Local 99% Winter Design Temperature: -10 to 4°F
6
NA
NA
NA
NA
NA
NA
NA
484
8
NA
NA
NA
NA
NA
NA
NA
494
10
NA
NA
NA
NA
NA
NA
NA
513
15
NA
NA
NA
NA
NA
NA
NA
586
20
NA
NA
NA
NA
NA
NA
NA
650
30
NA
NA
NA
NA
NA
NA
NA
805
50
NA
NA
NA
NA
NA
NA
NA
1,003
-11°F or Lower
Local 99% Winter Design Temperature: -11°F or Lower
Not recommended for any vent configurations
Note: See Figure B-19 in Appendix B for a map showing local 99 percent winter design temperatures in the United States.
For SI: °C = [(°F - 32]/1.8, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
These venting tables shall not be used where obstructions, as described in Section 503.15, are installed in the venting system. The installation of vents serving listed appliances with vent dampers shall be in accordance with the appliance manufacturer's instructions or in accordance with the following:
  1. The maximum capacity of the vent system shall be determined using the "NAT Max" column.
  2. The minimum capacity shall be determined as if the appliance were a fan-assisted appliance, using the "FAN Min" column to determine the minimum capacity of the vent system. Where the corresponding "FAN Min" is "NA," the vent configuration shall not be permitted and an alternative venting configuration shall be utilized.
Where the vent size determined from the tables is smaller than the appliance draft hood outlet or flue collar, the smaller size shall be permitted to be used provided that all of the following requirements are met:
  1. The total vent height (H) is at least 10 feet (3048 mm).
  2. Vents for appliance draft hood outlets or flue collars 12 inches (305 mm) in diameter or smaller are not reduced more than one table size.
  3. Vents for appliance draft hood outlets or flue collars larger than 12 inches (305 mm) in diameter are not reduced more than two table sizes.
  4. The maximum capacity listed in the tables for a fan-assisted appliance is reduced by 10 percent (0.90 × maximum table capacity).
  5. The draft hood outlet is greater than 4 inches (102 mm) in diameter. Do not connect a 3-inch-diameter (76 mm) vent to a 4-inch-diameter (102 mm) draft hood outlet. This provision shall not apply to fan-assisted appliances.
Single-appliance venting configurations with zero (0) lateral lengths in Tables 504.2(1), 504.2(2) and 504.2(5) shall not have elbows in the venting system. Single-appliance venting configurations with lateral lengths include two 90-degree (1.57 rad) elbows. For each additional elbow up to and including 45 degrees (0.79 rad), the maximum capacity listed in the venting tables shall be reduced by 5 percent. For each additional elbow greater than 45 degrees (0.79 rad) up to and including 90 degrees (1.57 rad), the maximum capacity listed in the venting tables shall be reduced by 10 percent. Where multiple offsets occur in a vent, the total lateral length of all offsets combined shall not exceed that specified in Tables 504.2(1) through 504.2(5).
Zero (0) lateral (L) shall apply only to a straight vertical vent attached to a top outlet draft hood or flue collar.
Sea-level input ratings shall be used when determining maximum capacity for high altitude installation. Actual input (derated for altitude) shall be used for determining minimum capacity for high altitude installation.
For appliances with more than one input rate, the minimum vent capacity (FAN Min) determined from the tables shall be less than the lowest appliance input rating, and the maximum vent capacity (FAN Max/NAT Max) determined from the tables shall be greater than the highest appliance rating input.
Listed corrugated metallic chimney liner systems in masonry chimneys shall be sized by using Table 504.2(1) or 504.2(2) for Type B vents with the maximum capacity reduced by 20 percent (0.80 ´ maximum capacity) and the minimum capacity as shown in Table 504.2(1) or 504.2(2). Corrugated metallic liner systems installed with bends or offsets shall have their maximum capacity further reduced in accordance with Section 504.2.3. The 20-percent reduction for corrugated metallic chimney liner systems includes an allowance for one long-radius 90-degree (1.57 rad) turn at the bottom of the liner.
Connections between chimney liners and listed double-wall connectors shall be made with listed adapters designed for such purpose.
Where the vertical vent has a larger diameter than the vent connector, the vertical vent diameter shall be used to determine the minimum vent capacity, and the connector diameter shall be used to determine the maximum vent capacity. The flow area of the vertical vent shall not exceed seven times the flow area of the listed appliance categorized vent area, flue collar area or draft hood outlet area unless designed in accordance with approved engineering methods.
Tables 504.2(1), 504.2(2), 504.2(3), 504.2(4) and 504.2(5) shall be used only for chimneys and vents not exposed to the outdoors below the roof line. A Type B vent or listed chimney lining system passing through an unused masonry chimney flue shall not be considered to be exposed to the outdoors. A Type B vent shall not be considered to be exposed to the outdoors where it passes through an unventilated enclosure or chase insulated to a value of not less than R8.

TABLE 504.2(3) in combination with Table 504.2(6) shall be used for clay-tile-lined exterior masonry chimneys, provided that all of the following are met:
  1. Vent connector is a Type B double wall.
  2. Vent connector length is limited to 11/2 feet for each inch (18 mm per mm) of vent connector diameter.
  3. The appliance is draft hood equipped.
  4. The input rating is less than the maximum capacity given by Table 504.2(3).
  5. For a water heater, the outdoor design temperature is not less than 5°F (-15°C).
  6. For a space-heating appliance, the input rating is greater than the minimum capacity given by Table 504.2(6).
Corrugated vent connectors shall be not smaller than the listed appliance categorized vent diameter, flue collar diameter or draft hood outlet diameter.
Vent connectors shall not be increased in size more than two sizes greater than the listed appliance categorized vent diameter, flue collar diameter or draft hood outlet diameter.
In a single run of vent or vent connector, different diameters and types of vent and connector components shall be permitted to be used, provided that all such sizes and types are permitted by the tables.
Draft hood conversion accessories for use with masonry chimneys venting listed Category I fan-assisted appliances shall be listed and installed in accordance with the manufacturer's installation instructions for such listed accessories.
Interpolation shall be permitted in calculating capacities for vent dimensions that fall between the table entries (see Example 3, Appendix B).
Extrapolation beyond the table entries shall not be permitted.
For vent heights less than 6 feet (1829 mm) and greater than shown in the tables, engineering methods shall be used to calculate vent capacities.
The application of Tables 504.3(1) through 504.3(7) shall be subject to the requirements of Sections 504.3.1 through 504.3.27.
TABLE 504.3(1)
TYPE B DOUBLE-WALL VENT
Number of Appliances
Two or more
Appliance Vent Connection
Type B double-wall connector
VENT CONNECTOR CAPACITY
VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER—(D) inches
3
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
1
22
37
26
35
66
46
46
106
72
58
164
104
77
225
142
92
296
185
109
376
237
128
466
289
2
23
41
31
37
75
55
48
121
86
60
183
124
79
253
168
95
333
220
112
424
282
131
526
345
3
24
44
35
38
81
62
49
132
96
62
199
139
82
275
189
97
363
248
114
463
317
134
575
386
8
1
22
40
27
35
72
48
49
114
76
64
176
109
84
243
148
100
320
194
118
408
248
138
507
303
2
23
44
32
36
80
57
51
128
90
66
195
129
86
269
175
103
356
230
121
454
294
141
564
358
3
24
47
36
37
87
64
53
139
101
67
210
145
88
290
198
105
384
258
123
492
330
143
612
402
10
1
22
43
28
34
78
50
49
123
78
65
189
113
89
257
154
106
341
200
125
436
257
146
542
314
2
23
47
33
36
86
59
51
136
93
67
206
134
91
282
182
109
374
238
128
479
305
149
596
372
3
24
50
37
37
92
67
52
146
104
69
220
150
94
303
205
111
402
268
131
515
342
152
642
417
15
1
21
50
30
33
89
53
47
142
83
64
220
120
88
298
163
110
389
214
134
493
273
162
609
333
2
22
53
35
35
96
63
49
153
99
66
235
142
91
320
193
112
419
253
137
532
323
165
658
394
3
24
55
40
36
102
71
51
163
111
68
248
160
93
339
218
115
445
286
140
565
365
167
700
444
20
1
21
54
31
33
99
56
46
157
87
62
246
125
86
334
171
107
436
224
131
552
285
158
681
347
2
22
57
37
34
105
66
48
167
104
64
259
149
89
354
202
110
463
265
134
587
339
161
725
414
3
23
60
42
35
110
74
50
176
116
66
271
168
91
371
228
113
486
300
137
618
383
164
764
466
30
1
20
62
33
31
113
59
45
181
93
60
288
134
83
391
182
103
512
238
125
649
305
151
802
372
2
21
64
39
33
118
70
47
190
110
62
299
158
85
408
215
105
535
282
129
679
360
155
840
439
3
22
66
44
34
123
79
48
198
124
64
309
178
88
423
242
108
555
317
132
706
405
158
874
494
50
1
19
71
36
30
133
64
43
216
101
57
349
145
78
477
197
97
627
257
120
797
330
144
984
403
2
21
73
43
32
137
76
45
223
119
59
358
172
81
490
234
100
645
306
123
820
392
148
1,014
478
3
22
75
48
33
141
86
46
229
134
61
366
194
83
502
263
103
661
343
126
842
441
151
1,043
538
100
1
18
82
37
28
158
66
40
262
104
53
442
150
73
611
204
91
810
266
112
1,038
341
135
1,285
417
2
19
83
44
30
161
79
42
267
123
55
447
178
75
619
242
94
822
316
115
1,054
405
139
1,306
494
3
20
84
50
31
163
89
44
272
138
57
452
109
78
627
272
97
834
355
118
1,069
455
142
1,327
555

COMMON VENT CAPACITY
VENT HEIGHT
(H)
(feet)
TYPE B DOUBLE-WALL COMMON VENT DIAMETER (D)—inches
4
5
6
7
8
9
10
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
92
81
65
140
116
103
204
161
147
309
248
200
404
314
260
547
434
335
672
520
410
8
101
90
73
155
129
114
224
178
163
339
275
223
444
348
290
602
480
378
740
577
465
10
110
97
79
169
141
124
243
194
178
367
299
242
477
377
315
649
522
405
800
627
495
15
125
112
91
195
164
144
283
228
206
427
352
280
556
444
365
753
612
465
924
733
565
20
136
123
102
215
183
160
314
255
229
475
394
310
621
499
405
842
688
523
1,035
826
640
30
152
138
118
244
210
185
361
297
266
547
459
360
720
585
470
979
808
605
1,209
975
740
50
167
153
134
279
244
214
421
353
310
641
547
423
854
706
550
1,164
977
705
1,451
1,188
860
100
175
163
NA
311
277
NA
489
421
NA
751
658
479
1,025
873
625
1,408
1,215
800
1,784
1,502
975
TABLE 504.3(1)—continued
TYPE B DOUBLE-WALL VENT
Number of Appliances
Two or more
Appliance Vent Connection
Type B double-wall connector
VENT CONNECTOR CAPACITY
VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
TYPE B DOUBLE-WALL VENT AND DIAMETER—(D) inches
12
14
16
18
20
22
24
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
2
174
764
496
223
1,046
653
281
1,371
853
346
1,772
1,080
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
180
897
616
230
1,231
827
287
1,617
1,081
352
2,069
1,370
NA
NA
NA
NA
NA
NA
NA
NA
NA
6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
8
2
186
822
516
238
1,126
696
298
1,478
910
365
1,920
1,150
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
192
952
644
244
1,307
884
305
1,719
1,150
372
2,211
1,460
471
2,737
1,800
560
3,319
2,180
662
3,957
2,590
6
198
1,050
772
252
1,445
1,072
313
1,902
1,390
380
2,434
1,770
478
3,018
2,180
568
3,665
2,640
669
4,373
3,130
10
2
196
870
536
249
1,195
730
311
1,570
955
379
2,049
1,205
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
201
997
664
256
1,371
924
318
1,804
1,205
387
2,332
1,535
486
2,887
1,890
581
3,502
2,280
686
4,175
2,710
6
207
1,095
792
263
1,509
1,118
325
1,989
1,455
395
2,556
1,865
494
3,169
2,290
589
3,849
2,760
694
4,593
3,270
15
2
214
967
568
272
1,334
790
336
1,760
1,030
408
2,317
1,305
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
221
1,085
712
279
1,499
1,006
344
1,978
1,320
416
2,579
1,665
523
3,197
2,060
624
3,881
2,490
734
4,631
2,960
6
228
1,181
856
286
1,632
1,222
351
2,157
1,610
424
2,796
2,025
533
3,470
2,510
634
4,216
3,030
743
5,035
3,600
20
2
223
1,051
596
291
1,443
840
357
1,911
1,095
430
2,533
1,385
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
230
1,162
748
298
1,597
1,064
365
2,116
1,395
438
2,778
1,765
554
3,447
2,180
661
4,190
2,630
772
5,005
3,130
6
237
1,253
900
307
1,726
1,288
373
2,287
1,695
450
2,984
2,145
567
3,708
2,650
671
4,511
3,190
785
5,392
3,790
30
2
216
1,217
632
286
1,664
910
367
2,183
1,190
461
2,891
1,540
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
223
1,316
792
294
1,802
1,160
376
2,366
1,510
474
3,110
1,920
619
3,840
2,365
728
4,861
2,860
847
5,606
3,410
6
231
1,400
952
303
1,920
1,410
384
2,524
1,830
485
3,299
2,340
632
4,080
2,875
741
4,976
3,480
860
5,961
4,150
50
2
206
1,479
689
273
2,023
1,007
350
2,659
1,315
435
3,548
1,665
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
213
1,561
860
281
2,139
1,291
359
2,814
1,685
447
3,730
2,135
580
4,601
2,633
709
5,569
3,185
851
6,633
3,790
6
221
1,631
1,031
290
2,242
1,575
369
2,951
2,055
461
3,893
2,605
594
4,808
3,208
724
5,826
3,885
867
6,943
4,620
100
2
192
1,923
712
254
2,644
1,050
326
3,490
1,370
402
4,707
1,740
NA
NA
NA
NA
NA
NA
NA
NA
NA
4
200
1,984
888
263
2,731
1,346
336
3,606
1,760
414
4,842
2,220
523
5,982
2,750
639
7,254
3,330
769
8,650
3,950
6
208
2,035
1,064
272
2,811
1,642
346
3,714
2,150
426
4,968
2,700
539
6,143
3,350
654
7,453
4,070
786
8,892
4,810
COMMON VENT CAPACITY
VENT HEIGHT
(H)
(feet)
TYPE B DOUBLE-WALL COMMON VENT DIAMETER—(D) inches
12
14
16
18
20
22
24
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
900
696
588
1,284
990
815
1,735
1,336
1,065
2,253
1,732
1,345
2,838
2,180
1,660
3,488
2,677
1970
4,206
3,226
2,390
8
994
773
652
1,423
1,103
912
1,927
1,491
1,190
2,507
1,936
1,510
3,162
2,439
1,860
3,890
2,998
2,200
4,695
3,616
2,680
10
1,076
841
712
1,542
1,200
995
2,093
1,625
1,300
2,727
2,113
1645
3,444
2,665
2,030
4,241
3,278
2,400
5,123
3,957
2,920
15
1,247
986
825
1,794
1,410
1,158
2,440
1,910
1,510
3,184
2,484
1,910
4,026
3,133
2,360
4,971
3,862
2,790
6,016
4,670
3,400
20
1,405
1,116
916
2,006
1,588
1,290
2,722
2,147
1,690
3,561
2,798
2,140
4,548
3,552
2,640
5,573
4,352
3,120
6,749
5,261
3,800
30
1,658
1,327
1,025
2,373
1,892
1,525
3,220
2,558
1,990
4,197
3,326
2,520
5,303
4,193
3,110
6,539
5,157
3,680
7,940
6,247
4,480
50
2,024
1,640
1,280
2,911
2,347
1,863
3,964
3,183
2,430
5,184
4,149
3,075
6,567
5,240
3,800
8,116
6,458
4,500
9,837
7,813
5,475
100
2,569
2,131
1,670
3,732
3,076
2,450
5,125
4,202
3,200
6,749
5,509
4,050
8,597
6,986
5,000
10,681
8,648
5,920
13,004
10,499
7,200
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.3(2)
TYPE B DOUBLE-WALL VENT
Number of Appliances
Two or more
Appliance Vent Connection
Single-wall metal connector
VENT CONNECTOR CAPACITY
VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
SINGLE-WALL METAL VENT CONNECTOR DIAMETER—(D) inches
3
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
1
NA
NA
26
NA
NA
46
NA
NA
71
NA
NA
102
207
223
140
262
293
183
325
373
234
447
463
286
2
NA
NA
31
NA
NA
55
NA
NA
85
168
182
123
215
251
167
271
331
219
334
422
281
458
524
344
3
NA
NA
34
NA
NA
62
121
131
95
175
198
138
222
273
188
279
361
247
344
462
316
468
574
385
8
1
NA
NA
27
NA
NA
48
NA
NA
75
NA
NA
106
226
240
145
285
316
191
352
403
244
481
502
299
2
NA
NA
32
NA
NA
57
125
126
89
184
193
127
234
266
173
293
353
228
360
450
292
492
560
355
3
NA
NA
35
NA
NA
64
130
138
100
191
208
144
241
287
197
302
381
256
370
489
328
501
609
400
10
1
NA
NA
28
NA
NA
50
119
121
77
182
186
110
240
253
150
302
335
196
372
429
252
506
534
308
2
NA
NA
33
84
85
59
124
134
91
189
203
132
248
278
183
311
369
235
381
473
302
517
589
368
3
NA
NA
36
89
91
67
129
144
102
197
217
148
257
299
203
320
398
265
391
511
339
528
637
413
15
1
NA
NA
29
79
87
52
116
138
81
177
214
116
238
291
158
312
380
208
397
482
266
556
596
324
2
NA
NA
34
83
94
62
121
150
97
185
230
138
246
314
189
321
411
248
407
522
317
568
646
387
3
NA
NA
39
87
100
70
127
160
109
193
243
157
255
333
215
331
438
281
418
557
360
579
690
437
20
1
49
56
30
78
97
54
115
152
84
175
238
120
233
325
165
306
425
217
390
538
276
546
664
336
2
52
59
36
82
103
64
120
163
101
182
252
144
243
346
197
317
453
259
400
574
331
558
709
403
3
55
62
40
87
107
72
125
172
113
190
264
164
252
363
223
326
476
294
412
607
375
570
750
457
30
1
47
60
31
77
110
57
112
175
89
169
278
129
226
380
175
296
497
230
378
630
294
528
779
358
2
51
62
37
81
115
67
117
185
106
177
290
152
236
397
208
307
521
274
389
662
349
541
819
425
3
54
64
42
85
119
76
122
193
120
185
300
172
244
412
235
316
542
309
400
690
394
555
855
482
50
1
46
69
34
75
128
60
109
207
96
162
336
137
217
460
188
284
604
245
364
768
314
507
951
384
2
49
71
40
79
132
72
114
215
113
170
345
164
226
473
223
294
623
293
376
793
375
520
983
458
3
52
72
45
83
136
82
119
221
123
178
353
186
235
486
252
304
640
331
387
816
423
535
1,013
518
100
1
45
79
34
71
150
61
104
249
98
153
424
140
205
585
192
269
774
249
345
993
321
476
1,236
393
2
48
80
41
75
153
73
110
255
115
160
428
167
212
593
228
279
788
299
358
1,011
383
490
1,259
469
3
51
81
46
79
157
85
114
260
129
168
433
190
222
603
256
289
801
339
368
1,027
431
506
1,280
527
COMMON VENT CAPACITY
VENT HEIGHT
(H)
(feet)
TYPE B DOUBLE-WALL COMMON VENT DIAMETER— (D) inches
4
5
6
7
8
9
10
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
NA
78
64
NA
113
99
200
158
144
304
244
196
398
310
257
541
429
332
665
515
407
8
NA
87
71
NA
126
111
218
173
159
331
269
218
436
342
285
592
473
373
730
569
460
10
NA
94
76
163
137
120
237
189
174
357
292
236
467
369
309
638
512
398
787
617
487
15
121
108
88
189
159
140
275
221
200
416
343
274
544
434
357
738
599
456
905
718
553
20
131
118
98
208
177
156
305
247
223
463
383
302
606
487
395
824
673
512
1,013
808
626
30
145
132
113
236
202
180
350
286
257
533
446
349
703
570
459
958
790
593
1,183
952
723
50
159
145
128
268
233
208
406
337
296
622
529
410
833
686
535
1,139
954
689
1,418
1,157
838
100
166
153
NA
297
263
NA
469
398
NA
726
633
464
999
846
606
1,378
1,185
780
1,741
1,459
948
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.

TABLE 504.3(3)
MASONRY CHIMNEY
Number of Appliances
Two or more
Appliance Vent Connection
Type B double-wall connector
VENT CONNECTOR CAPACITY
VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
TYPE B DOUBLE-WALL VENT CONNECTOR DIAMETER—(D) inches
3
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
1
24
33
21
39
62
40
52
106
67
65
194
101
87
274
141
104
370
201
124
479
253
145
599
319
2
26
43
28
41
79
52
53
133
85
67
230
124
89
324
173
107
436
232
127
562
300
148
694
378
3
27
49
34
42
92
61
55
155
97
69
262
143
91
369
203
109
491
270
129
633
349
151
795
439
8
1
24
39
22
39
72
41
55
117
69
71
213
105
94
304
148
113
414
210
134
539
267
156
682
335
2
26
47
29
40
87
53
57
140
86
73
246
127
97
350
179
116
473
240
137
615
311
160
776
394
3
27
52
34
42
97
62
59
159
98
75
269
145
99
383
206
119
517
276
139
672
358
163
848
452
10
1
24
42
22
38
80
42
55
130
71
74
232
108
101
324
153
120
444
216
142
582
277
165
739
348
2
26
50
29
40
93
54
57
153
87
76
261
129
103
366
184
123
498
247
145
652
321
168
825
407
3
27
55
35
41
105
63
58
170
100
78
284
148
106
397
209
126
540
281
147
705
366
171
893
463
15
1
24
48
23
38
93
44
54
154
74
72
277
114
100
384
164
125
511
229
153
658
297
184
824
375
2
25
55
31
39
105
55
56
174
89
74
299
134
103
419
192
128
558
260
156
718
339
187
900
432
3
26
59
35
41
115
64
57
189
102
76
319
153
105
448
215
131
597
292
159
760
382
190
960
486
20
1
24
52
24
37
102
46
53
172
77
71
313
119
98
437
173
123
584
239
150
752
312
180
943
397
2
25
58
31
39
114
56
55
190
91
73
335
138
101
467
199
126
625
270
153
805
354
184
1,011
452
3
26
63
35
40
123
65
57
204
104
75
353
157
104
493
222
129
661
301
156
851
396
187
1,067
505
30
1
24
54
25
37
111
48
52
192
82
69
357
127
96
504
187
119
680
255
145
883
337
175
1,115
432
2
25
60
32
38
122
58
54
208
95
72
376
145
99
531
209
122
715
287
149
928
378
179
1,171
484
3
26
64
36
40
131
66
56
221
107
74
392
163
101
554
233
125
746
317
152
968
418
182
1,220
535
50
1
23
51
25
36
116
51
51
209
89
67
405
143
92
582
213
115
798
294
140
1,049
392
168
1,334
506
2
24
59
32
37
127
61
53
225
102
70
421
161
95
604
235
118
827
326
143
1,085
433
172
1,379
558
3
26
64
36
39
135
69
55
237
115
72
435
80
98
624
260
121
854
357
147
1,118
474
176
1,421
611
100
1
23
46
24
35
108
50
49
208
92
65
428
155
88
640
237
109
907
334
134
1,222
454
161
1,589
596
2
24
53
31
37
120
60
51
224
105
67
444
174
92
660
260
113
933
368
138
1,253
497
165
1,626
651
3
25
59
35
38
130
68
53
237
118
69
458
193
94
679
285
116
956
399
141
1,282
540
169
1,661
705
COMMON VENT CAPACITY
VENT HEIGHT
(H)
(feet)
MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)
12
19
28
38
50
63
78
113
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
NA
74
25
NA
119
46
NA
178
71
NA
257
103
NA
351
143
NA
458
188
NA
582
246
1,041
853
NA
8
NA
80
28
NA
130
53
NA
193
82
NA
279
119
NA
384
163
NA
501
218
724
636
278
1,144
937
408
10
NA
84
31
NA
138
56
NA
207
90
NA
299
131
NA
409
177
606
538
236
776
686
302
1,226
1,010
454
15
NA
NA
36
NA
152
67
NA
233
106
NA
334
152
523
467
212
682
611
283
874
781
365
1,374
1,156
546
20
NA
NA
41
NA
NA
75
NA
250
122
NA
368
172
565
508
243
742
668
325
955
858
419
1,513
1,286
648
30
NA
NA
NA
NA
NA
NA
NA
270
137
NA
404
198
615
564
278
816
747
381
1,062
969
496
1,702
1,473
749
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
620
328
879
831
461
1,165
1,089
606
1,905
1,692
922
100
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
348
NA
NA
499
NA
NA
669
2,053
1,921
1,058
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.3(4)
MASONRY CHIMNEY
Number of Appliances
Two or more
Appliance Vent Connection
Single-wall metal connector
VENT CONNECTOR CAPACITY
VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
SINGLE-WALL METAL VENT CONNECTOR DIAMETER (D)—inches
3
4
5
6
7
8
9
10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU/H
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
FAN
NAT
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
Min
Max
Max
6
1
NA
NA
21
NA
NA
39
NA
NA
66
179
191
100
231
271
140
292
366
200
362
474
252
499
594
316
2
NA
NA
28
NA
NA
52
NA
NA
84
186
227
123
239
321
172
301
432
231
373
557
299
509
696
376
3
NA
NA
34
NA
NA
61
134
153
97
193
258
142
247
365
202
309
491
269
381
634
348
519
793
437
8
1
NA
NA
21
NA
NA
40
NA
NA
68
195
208
103
250
298
146
313
407
207
387
530
263
529
672
331
2
NA
NA
28
NA
NA
52
137
139
85
202
240
125
258
343
177
323
465
238
397
607
309
540
766
391
3
NA
NA
34
NA
NA
62
143
156
98
210
264
145
266
376
205
332
509
274
407
663
356
551
838
450
10
1
NA
NA
22
NA
NA
41
130
151
70
202
225
106
267
316
151
333
434
213
410
571
273
558
727
343
2
NA
NA
29
NA
NA
53
136
150
86
210
255
128
276
358
181
343
489
244
420
640
317
569
813
403
3
NA
NA
34
97
102
62
143
166
99
217
277
147
284
389
207
352
530
279
430
694
363
580
880
459
15
1
NA
NA
23
NA
NA
43
129
151
73
199
271
112
268
376
161
349
502
225
445
646
291
623
808
366
2
NA
NA
30
92
103
54
135
170
88
207
295
132
277
411
189
359
548
256
456
706
334
634
884
424
3
NA
NA
34
96
112
63
141
185
101
215
315
151
286
439
213
368
586
289
466
755
378
646
945
479
20
1
NA
NA
23
87
99
45
128
167
76
197
303
117
265
425
169
345
569
235
439
734
306
614
921
347
2
NA
NA
30
91
111
55
134
185
90
205
325
136
274
455
195
355
610
266
450
787
348
627
986
443
3
NA
NA
35
96
119
64
140
199
103
213
343
154
282
481
219
365
644
298
461
831
391
639
1,042
496
30
1
NA
NA
24
86
108
47
126
187
80
193
347
124
259
492
183
338
665
250
430
864
330
600
1,089
421
2
NA
NA
31
91
119
57
132
203
93
201
366
142
269
518
205
348
699
282
442
908
372
613
1,145
473
3
NA
NA
35
95
127
65
138
216
105
209
381
160
277
540
229
358
729
312
452
946
412
626
1,193
524
50
1
NA
NA
24
85
113
50
124
204
87
188
392
139
252
567
208
328
778
287
417
1,022
383
582
1,302
492
2
NA
NA
31
89
123
60
130
218
100
196
408
158
262
588
230
339
806
320
429
1,058
425
596
1,346
545
3
NA
NA
35
94
131
68
136
231
112
205
422
176
271
607
255
349
831
351
440
1,090
466
610
1,386
597
100
1
NA
NA
23
84
104
49
122
200
89
182
410
151
243
617
232
315
875
328
402
1,181
444
560
1,537
580
2
NA
NA
30
88
115
59
127
215
102
190
425
169
253
636
254
326
899
361
415
1,210
488
575
1,570
634
3
NA
NA
34
93
124
67
133
228
115
199
438
188
262
654
279
337
921
392
427
1,238
529
589
1,604
687
COMMON VENT CAPACITY
VENT HEIGHT
(H)
(feet)
MINIMUM INTERNAL AREA OF MASONRY CHIMNEY FLUE (square inches)
12
19
28
38
50
63
78
113
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6
NA
NA
25
NA
118
45
NA
176
71
NA
255
102
NA
348
142
NA
455
187
NA
579
245
NA
846
NA
8
NA
NA
28
NA
128
52
NA
190
81
NA
276
118
NA
380
162
NA
497
217
NA
633
277
1,136
928
405
10
NA
NA
31
NA
136
56
NA
205
89
NA
295
129
NA
405
175
NA
532
234
171
680
300
1,216
1,000
450
15
NA
NA
36
NA
NA
66
NA
230
105
NA
335
150
NA
400
210
677
602
280
866
772
360
1,359
1,139
540
20
NA
NA
NA
NA
NA
74
NA
247
120
NA
362
170
NA
503
240
765
661
321
947
849
415
1,495
1,264
640
30
NA
NA
NA
NA
NA
NA
NA
NA
135
NA
398
195
NA
558
275
808
739
377
1,052
957
490
1,682
1,447
740
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
612
325
NA
821
456
1,152
1,076
600
1,879
1,672
910
100
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
494
NA
NA
663
2,006
1,885
1,046
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.

TABLE 504.3(5)
SINGLE-WALL METAL PIPE OR TYPE ASBESTOS CEMENT VENT
Number of Appliances
Two or more
Draft hood-equipped
Appliance Vent Connection
Direct to pipe or vent
VENT CONNECTOR CAPACITY
TOTAL VENT HEIGHT
(H)
(feet)
CONNECTOR
RISE
(R)
(feet)
VENT CONNECTOR DIAMETER—(D) inches
3
4
5
6
7
8
MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6-8
1
21
40
68
102
146
205
2
28
53
86
124
178
235
3
34
61
98
147
204
275
15
1
23
44
77
117
179
240
2
30
56
92
134
194
265
3
35
64
102
155
216
298
30 and up
1
25
49
84
129
190
270
2
31
58
97
145
211
295
3
36
68
107
164
232
321

COMMON VENT CAPACITY
TOTAL VENT HEIGHT
(H)
(feet)
COMMON VENT DIAMETER—(D) inches
4
5
6
7
8
10
12
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU/H
6
48
78
111
155
205
320
NA
8
55
89
128
175
234
365
505
10
59
95
136
190
250
395
560
15
71
115
168
228
305
480
690
20
80
129
186
260
340
550
790
30
NA
147
215
300
400
650
940
50
NA
NA
NA
360
490
810
1,190
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.

TABLE 504.3(6a)
EXTERIOR MASONRY CHIMNEY
Number of
Appliances
Two or more
Appliance
Type
NAT + NAT
Combined Appliance Maximum
Input Rating in Thousands of Btu per Hour
VENT HEIGHT
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12
19
28
38
50
63
78
113
6
25
46
71
103
143
188
246
NA
8
28
53
82
119
163
218
278
408
10
31
56
90
131
177
236
302
454
15
NA
67
106
152
212
283
365
546
20
NA
NA
NA
NA
NA
325
419
648
30
NA
NA
NA
NA
NA
NA
496
749
50
NA
NA
NA
NA
NA
NA
NA
922
100
NA
NA
NA
NA
NA
NA
NA
NA
TABLE 504.3(6b)
EXTERIOR MASONRY CHIMNEY
Number of
Appliances
Two or more
Appliance
Type
NAT + NAT
Appliance Vent Connection
Type B double-wall connector
Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
VENT HEIGHT
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12
19
28
38
50
63
78
113
37°F or Greater
Local 99% Winter Design Temperature: 37°F or Greater
6
0
0
0
0
0
0
0
NA
8
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
15
NA
0
0
0
0
0
0
0
20
NA
NA
NA
NA
NA
184
0
0
30
NA
NA
NA
NA
NA
393
334
0
50
NA
NA
NA
NA
NA
NA
NA
579
100
NA
NA
NA
NA
NA
NA
NA
NA
27 to 36°F
Local 99% Winter Design Temperature: 27 to 36°F
6
0
0
68
NA
NA
180
212
NA
8
0
0
82
NA
NA
187
214
263
10
0
51
NA
NA
NA
201
225
265
15
NA
NA
NA
NA
NA
253
274
305
20
NA
NA
NA
NA
NA
307
330
362
30
NA
NA
NA
NA
NA
NA
445
485
50
NA
NA
NA
NA
NA
NA
NA
763
100
NA
NA
NA
NA
NA
NA
NA
NA
TABLE 504.3(6b)
EXTERIOR MASONRY CHIMNEY—continued

Minimum Allowable Input Rating of
Space-Heating Appliance in Thousands of Btu per Hour
VENT HEIGHT
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12
19
28
38
50
63
78
113
17 to 26°F
Local 99% Winter Design Temperature: 17 to 26°F
6
NA
NA
NA
NA
NA
NA
NA
NA
8
NA
NA
NA
NA
NA
NA
264
352
10
NA
NA
NA
NA
NA
NA
278
358
15
NA
NA
NA
NA
NA
NA
331
398
20
NA
NA
NA
NA
NA
NA
387
457
30
NA
NA
NA
NA
NA
NA
NA
581
50
NA
NA
NA
NA
NA
NA
NA
862
100
NA
NA
NA
NA
NA
NA
NA
NA
5 to 16°F
Local 99% Winter Design Temperature: 5 to 16°F
6
NA
NA
NA
NA
NA
NA
NA
NA
8
NA
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
NA
430
15
NA
NA
NA
NA
NA
NA
NA
485
20
NA
NA
NA
NA
NA
NA
NA
547
30
NA
NA
NA
NA
NA
NA
NA
682
50
NA
NA
NA
NA
NA
NA
NA
NA
100
NA
NA
NA
NA
NA
NA
NA
NA
4°F or Lower
Local 99% Winter Design Temperature: 4°F or Lower
Not recommended for any vent configurations
Note: See Figure B-19 in Appendix B for a map showing local 99 percent winter design temperatures in the United States.
For SI: °C = [(°F - 32]/1.8, 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 foot = 304.8 mm, 1 British thermal unit per hour = 0.2931 W.
TABLE 504.3(7a)
EXTERIOR MASONRY CHIMNEY
Number of
Appliances
Two or more
Appliance
Type
FAN + NAT
Appliance Vent Connection
Type B double-wall connector
Combined Appliance Maximum
Input Rating in Thousands of Btu per Hour
VENT HEIGHT
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12
19
28
38
50
63
78
113
6
74
119
178
257
351
458
582
853
8
80
130
193
279
384
501
636
937
10
84
138
207
299
409
538
686
1,010
15
NA
152
233
334
467
611
781
1,156
20
NA
NA
250
368
508
668
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