Chapter 1 Administration

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Ventilation Air

Chapter 5 Exhaust Systems

Chapter 6 Duct Systems

Chapter 7 Combustion Air

Chapter 8 Chimneys and Vents

Chapter 9 Installation of Specific Appliances

Chapter 10 Boilers and Pressure Vessels

Chapter 11 Refrigeration

Chapter 12 Hydronics

Chapter 13 Fuel Gas Piping

Chapter 14 Process Piping

Chapter 15 Solar Energy Systems

Chapter 16 Stationary Power Plants

Chapter 17 Referenced Standards

Appendices [PDF]

Appendix A Residential Plan Examiner Review Form for HVAC System Design

Appendix B Procedures to be Followed to Place Gas Equipment in Operation

Appendix C Installation and Testing of Oil (Liquid) Fuel-Fired Equipment

Appendix D Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks

Appendix E Sustainable Practices

Appendix F Sizing of Venting Systems and Outdoor Combustion and Ventilation Opening Design

Appendix G Example Calculation of Outdoor Air Rate

The requirements of this chapter shall govern the venting of fuel-burning appliances.
Low-heat and medium-heat gas appliances shall be vented in accordance with this chapter. Other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards.
Appliances fueled by fuels other than gas shall be vented in accordance with NFPA 211 and the appliance manufacturer's instructions.
Type B and Type B-W gas vents shall comply with UL 441, Type L gas vents shall comply with UL 641.
Listed vents shall be installed in accordance with this chapter and the manufacturer's installation instructions. [NFPA 54:12.2.1]
Appliance vents shall not discharge into a space enclosed by screens having openings less than 14 of an inch (6.4 mm) mesh.
Except as permitted in Section 802.2.1 through Section 802.2.5, appliances shall be connected to venting systems. [NFPA 54:12.3.1]
The following appliances shall not be required to be vented:
  1. Listed ranges.
  2. Built-in domestic cooking units listed and marked for optional venting.
  3. Listed hot plates and listed laundry stoves.
  4. Listed Type 1 clothes dryers exhausted in accordance with Section 504.4.
  5. A single listed booster-type (automatic instantaneous) water heater, where designed and used solely for the sanitizing rinse requirements of a dishwashing machine, provided that the appliance is installed with the draft hood in place and unaltered, where a draft hood is required, in a commercial kitchen having a mechanical exhaust system; where installed in this manner, the draft hood outlet shall not be less than 36 inches (914 mm) vertically and 6 inches (152 mm) horizontally from a surface other than the appliance.
  6. Listed refrigerators.
  7. Counter appliances.
  8. Room heaters listed for unvented use.
  9. Direct gas-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 or gas lights. [NFPA 54:12.3.2]
    Where appliances in Section 802.2.1(5) through Section 802.2.1(11) are installed so the aggregate input rating exceeds 20 British thermal units per hour per cubic foot [(Btu/h)/ft3] (0.21 kW/m3) of room or space in which it is installed, one or more shall be provided with venting systems or other approved means for conveying the vent gases to the outdoors so the aggregate input rating of the remaining unvented appliances do not exceed 20 [(Btu/h)/ft3] (0.21 kW/m3). Where the calculation includes the volume of an adjacent room or space, the room or space in which the appliance is installed shall be directly connected to the adjacent room or space by a doorway, archway, or other opening of comparable size that cannot be closed. [NFPA 54:12.3.2.1, 12.3.2.2]
Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications and to vent industrial appliances, particularly where the process itself requires fume disposal. [NFPA 54:12.3.3]
The operation of industrial appliances such that its flue gases are discharged directly into a large and well-ventilated space shall be permitted. [NFPA 54:12.3.4]
Listed direct-vent appliances shall be installed in accordance with the manufacturer's installation instructions and Section 802.8.2. [NFPA 54:12.3.5]
Appliances incorporating integral venting means shall be installed in accordance with the manufacturer's installation instructions, Section 802.8, and Section 802.8.1. [NFPA 54:12.3.6]
Venting systems shall be designed and constructed to convey flue and vent gases to the outdoors. [NFPA 54:12.1]
A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer's instructions. [NFPA 54:12.4.1]
Appliances required to be vented shall be connected to a venting system designed and installed in accordance with the provisions of Section 802.4 through Section 802.15. [NFPA 54:12.4.2]
Mechanical draft systems shall be listed and installed in accordance with both the appliance and the mechanical draft system manufacturer's installation instructions. [NFPA 54:12.4.3.1]
Appliances requiring venting shall be permitted to be vented by means of mechanical draft systems of either forced or induced draft design. [NFPA 54:12.4.3.2]

Exception: Incinerators.
Forced draft systems and 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. [NFPA 54:12.4.3.3]
Vent connectors serving appliances vented by natural draft shall not be connected into mechanical draft systems operating under positive pressure. [NFPA 54:12.4.3.4]
Where a mechanical draft system is employed, provision shall be made to prevent the flow of gas to the main burners where the draft system is not performing so as to satisfy the operating requirements of the appliance for safe performance. [NFPA 54:12.4.3.5]
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 802.8 and Section 802.8.1. [NFPA 54:12.4.3.6]
Ventilating hoods and exhaust systems shall be permitted to be used to vent appliances installed in commercial applications. [NFPA 54:12.4.4.1]
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 where the damper is open to a position to properly vent the appliance and where the power means of exhaust is in operation. [NFPA 54:12.4.4.2]
Venting systems shall not extend into or pass through a fabricated air duct or furnace plenum. [NFPA 54:12.4.5.1]
The type of venting system to be used shall be in accordance with Table 802.4. [NFPA 54:12.5.1]

TABLE 802.4
TYPE OF VENTING SYSTEM TO BE USED
[NFPA 54: TABLE 12.5.1]
APPLIANCES TYPE OF VENTING SYSTEM
Listed Category I appliance Type B gas vent (Section 802.6)
Listed appliance equipped with
draft hood
Chimney (Section 802.5)
Appliance listed for use with
Type B gas vent
Single-wall metal pipe
(Section 802.7)
Listed chimney lining system for
gas venting (Section 802.5.3)
Special gas vent listed for this
appliance (Section 802.4.3)
Listed vented wall furnaces Type B-W gas vent (Section
802.6, Section 907.0)
Category II appliance
Category III appliance
Category IV appliance
As specified or furnished by
manufacturers of listed appliance
(Section 802.4.1 and
Section 802.4.3)
Incinerators, outdoors Single-wall metal pipe (Section
802.7, Section 802.7.2)
Incinerators, outdoors

Appliance that is capable of being
converted to use of solid fuel

Unlisted combination gas- and oil-
burning appliance

Combination gas- and solid-fuel
burning appliance

Appliance listed for use with
chimneys only

Unlisted appliance
Chimney (Section 802.5)
Listed combination gas- and oil-
burning appliance
Type L vent (Section 802.6) or
chimney (Section 802.5)
Decorative appliance in vented
fireplace
Chimney (Section 911.2)
Gas-fired toilets Single-wall metal pipe
(Section 802.7, Section 930.3)
Direct-vent appliance See Section 802.2.4
Appliance with integral vent See Section 802.2.5
Plastic piping used for venting appliances listed for use with such venting materials shall be approved. [NFPA 54:12.5.2]
Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer's installation instructions. Where primer is required, it shall be of a contrasting color. [NFPA 54:12.5.3]
Special gas vents shall be listed and installed in accordance with the special gas vent manufacturer's installation instructions. [NFPA 54:12.5.4]
Chimneys shall be installed in accordance with Section 802.5.1 through Section 802.5.3.
Factory-built chimneys shall be installed in accordance with the manufacturer's installation instructions. Factory-built chimneys used to vent appliances that operate at positive vent pressure shall be listed for such application. [NFPA 54:12.6.1.1]
Decorative shrouds addressed in Section 802.5.4.3 shall be listed or labeled in accordance with UL 103 for factory-built residential chimneys, UL 127 for factory-built fireplaces, or UL 1482 tor solid-fuel room heaters.
Factory-built chimneys shall comply with the requirements of UL 103 or UL 959. Factory-built chimneys for use with wood-burning appliances shall comply with the Type HT requirements of UL 103. [NFPA 211:6.1.3.1, 6.1.3.2]
Metal chimneys shall be built and installed in accordance with NFPA 211. [NFPA 54:12.6.1.2]
Masonry chimneys shall be built and installed in accordance with NFPA 211 and lined with approved clay flue lining, a listed chimney lining system, or other approved material that resists corrosion, erosion, softening, or cracking from vent gases at temperatures not exceeding 1800°F (982°C).

Exception: Masonry chimney flues lined with a chimney lining system specifically listed for use with listed appliances with draft hoods, Category I appliances, and other appliances listed for use with Type B vents shall be permitted. 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." [NFPA 54:12.6.1.3]
A chimney for a residential-type or low-heat appliance shall extend not less than 3 feet (914 mm) above the highest point where it passes through a roof of a building and not less than 2 feet (610 mm) higher than a portion of a building within a horizontal distance of 10 feet (3048 mm). (See Figure 802.5.4) [NFPA 54:12.6.2.1]
For SI units: 1 foot = 304.8 mm
FIGURE 802.5.4
TYPICAL TERMINATION LOCATIONS FOR
CHIMNEYS AND SINGLE-WALL METAL PIPES SERVING
RESIDENTIAL-TYPE AND LOW-HEAT APPLIANCE
[NFPA 54: FIGURE A.12.6.2.1]
A chimney for a medium-heat appliance shall extend not less than 10 feet (3048 mm) above a portion of a building within 25 feet (7620 mm). [NFPA 54:12.6.2.2]
A chimney shall extend not less than 5 feet (1524 mm) above the highest connected appliance draft hood outlet or flue collar. [NFPA 54:12.6.2.3]
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. [NFPA 54:12.6.2.4]
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 in accordance with one of the following methods [NFPA 54:12.6.3.1]:
  1. Section 803.0. [NFPA 54:12.6.3.1(1)]
  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 or exceeding seven times the draft hood outlet area. [NFPA 54:12.6.3.1(2)]
  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, or exceeding seven times the smallest draft hood outlet area. [NFPA 54:12.6.3.1(3)]
  4. Other approved engineering methods. [NFPA 54:12.6.3.1(5)]
  5. Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods. [NFPA 54:12.6.3.1(4)]
This inspection shall be made after chimneys, vents, or parts thereof, authorized by the permit, have been installed and before such vent or part thereof has been covered or concealed.
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 shall be cleaned where previously used for venting solid- or liquid-fuel-burning appliances or fireplaces. [NFPA 54:12.6.4.1]
Chimneys shall be lined in accordance with NFPA 211.

Exception: Existing chimneys shall be permitted to have their use continued where an appliance is replaced by an appliance of similar type, input rating, and efficiency, where the chimney is in accordance with Section 802.5.7, and the sizing of the chimney is in accordance with Section 802.5.5. [NFPA 54:12.6.4.2]
Cleanouts shall be examined to determine that they will remain tightly closed where not in use. [NFPA 54:12.6.4.3]
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 in accordance with NFPA 211, and shall be approved for the appliances to be attached. [NFPA 54:12.6.4.4]
An appliance shall not be connected to a chimney flue serving a separate appliance designed to burn solid fuel. [NFPA 54:12.6.5.1]
Where one chimney 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 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 gas appliance is automatically controlled, it shall be equipped with a safety shutoff device. [NFPA 54:12.6.5.2]
A listed combination gas-and solid-fuel-burning appliance connected to a single chimney flue shall be 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. [NFPA 54:12.6.5.3]
A single chimney flue serving a listed combination gas- and oil-burning appliance shall be sized to properly vent the appliance. [NFPA 54:12.6.5.4]
Portions of chimneys shall be supported for the design and weight of the materials employed. Listed factory-built chimneys shall be supported and spaced in accordance with the manufacturer's instructions. [NFPA 54:12.6.6]
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 be installed so its upper edge is not less than 6 inches (152 mm) below the lower edge of the lowest chimney inlet opening. [NFPA 54:12.6.7]
The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry chimney shall not be used to vent another appliance.

Exception: The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer's instructions. [NFPA 54:12.6.8.1]
The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry, metal or factory-built chimney flue shall not be used to supply combustion air.

Exception: Direct-vent appliances designed for installation in a solid-fuel-burning fireplace where installed in accordance with the manufacturer's installation instructions. [NFPA 54:12.6.8.2]
Gas vents shall be installed in accordance with the manufacturer's installation instructions. [NFPA 54:12.7.1(1)]
Screws, rivets, and other fasteners shall not penetrate the inner wall of double wall gas vents, except at the transition from the appliance draft hood outlet, flue collar, or single wall metal connector to a double wall vent. [NFPA 54:12.7.1(4)]
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 802.6.2 and Table 802.6.2. 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 a portion of a building within 10 feet (3048 mm) horizontally.
  2. Industrial appliances as provided in Section 802.2.3.
  3. Direct-vent systems as provided in Section 802.2.4.
  4. Appliance with integral vents as provided in Section 802.2.5.
  5. Mechanical draft systems as provided in Section 802.3.3.
  6. Ventilating hoods and exhaust systems as provided in Section 802.3.4. [NFPA 54:12.7.2(1)]
FIGURE 802.6.2
GAS VENT TERMINATION LOCATIONS FOR LISTED CAPS 12
INCHES OR LESS IN SIZE NOT LESS THAN 8 FEET FROM A
VERTICAL WALL
[NFPA 54: FIGURE 12.7.2]

TABLE 802.6.2
ROOF PITCH HEIGHT
[NFPA 54: TABLE 12.7.2]
ROOF PITCH H (minimum) (feet)
Flat to 612 1.0
Over 612 to 712 1.25
Over 712 to 812 1.5
Over 812 to 912 2.0
Over 912 to 1012 2.5
Over 1012 to 1112 3.25
Over 1112 to 1212 4.0
Over 1212 to 1412 5.0
Over 1412 to 1612 6.0
Over 1612 to 1812 7.0
Over 1812 to 2012 7.5
Over 2012 to 2112 8.0
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
A Type B or a Type L gas vent shall terminate not less than 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar. [NFPA 54:12.7.2(2)]
A Type B-W gas vent shall terminate not less than 12 feet (3658 mm) in vertical height above the bottom of the wall furnace. [NFPA 54:12.7.2(3)]
A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 802.2.4 and Section 802.3.3. [NFPA 54:12.7.2(4)]
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 the manufacturer's installation instructions. [NFPA 54:12.7.2(5)]
A gas vent shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly. [NFPA 54:12.7.2(6)]
A gas vent shall terminate not less than 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.2(7)]
Where a vent passes through an insulated assembly, an approved metal shield shall be installed between the vent and insulation. The shield shall extend not less than 2 inches (51 mm) above the insulation and be secured to the structure in accordance with the manufacturer's installation instructions.
Venting systems shall be sized and constructed in accordance with Section 803.0 or other approved engineering methods and the gas vent and appliance manufacturer's instructions. [NFPA 54:12.7.3]
The sizing of natural draft venting systems serving one or more listed appliances equipped with a draft hood or appliances listed for use with a Type B gas vent, installed in a single story of a building, shall be in accordance with one of the following:
  1. The provisions of Section 803.0.
  2. Vents serving fan-assisted combustion system appliances, or combinations of fan-assisted combustion system and draft hood-equipped appliances shall be sized in accordance with Section 803.0 or other approved engineering methods.
  3. 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 or exceeding seven times the draft hood outlet area.
  4. 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 or exceeding seven times the smaller draft hood outlet area.
  5. Approved engineering practices. [NFPA 54:12.7.3.1]
Type B or Type L vents shall extend in a vertical direction with offsets not exceeding 45 degrees (0.79 rad), except that a vent system having not more than one 60 degree (1.05 rad) offset shall be permitted. An 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 not exceed 75 percent of the vertical height of the vent. [NFPA 54:12.7.3.2]
The sizing of gas vents for Category II, Category III, and Category IV appliances shall be in accordance with the appliance manufacturer's instructions. [NFPA 54:12.7.3.3]
Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods. [NFPA 54:12.7.3.4]
A common vent shall be permitted in multistory installations to vent Category I appliances located on more than one floor level, provided 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. [NFPA 54:12.7.4.1]
Appliances connected to the common vent shall be located in rooms separated from an 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 802.6.4.1) [NFPA 54:12.7.4.2]
FIGURE 802.6.4.1
PLAN VIEW OF PRACTICAL SEPARATION METHOD FOR
MULTISTORY GAS VENTING
[NFPA 54: FIGURE A.12.7.4.2]
The size of the connectors and common segments of multistory venting systems for appliances listed for use with a Type B double-wall gas vent shall be in accordance with Table 803.2(1), provided the following apply:
  1. The 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 802.6.4.2)
  2. The size of the connector for a segment is determined from the appliance's gas input rate and connector rise, and shall not be smaller than the draft hood outlet or flue collar size.
  3. The size of the common vertical vent segment, and of the interconnection tee at the base of that segment, shall be based on the total appliance's gas input rate entering that segment and its total height. [NFPA 54:12.7.4.3]
FIGURE 802.6.4.2
USE OF MANIFOLDED COMMON VENT CONNECTOR
[NFPA 54: FIGURE F.1(k)]
Gas vents shall be supported and spaced in accordance with the manufacturer's installation instructions. [NFPA 54:12.7.5]
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 label shall read: "This gas vent is for appliances that burn gas. Do not connect to solid or liquid-fuel-burning appliances or incinerators." The Authority Having Jurisdiction shall determine whether its area constitutes such a locality. [NFPA 54:12.7.6]
Single-wall metal pipe shall be constructed of galvanized sheet steel not less than 0.0304 of an inch (0.7722 mm) thick or of other approved, noncombustible, corrosion-resistant material. [NFPA 54:12.8.1]
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). [NFPA 54:12.8.2]
The termination of single-wall metal pipe shall comply with the following requirements:
  1. Single-wall metal pipe shall terminate not less than 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood outlet or flue collar.
  2. Single-wall metal pipe shall extend not less than 2 feet (610 mm) above the highest point where it passes through a roof of a building and not less than 2 feet (610 mm) exceeding a portion of a building within a horizontal distance of 10 feet (3048 mm). (See Figure 802.5.4)
  3. An approved cap or roof assembly shall be attached to the terminus of a single-wall metal pipe. [NFPA 54:12.8.3]
Single-wall metal pipe shall not be used as a vent in dwellings and residential occupancies. [NFPA 54:12.8.4.1]
Single-wall metal pipe shall be used for runs directly from the space in which the appliance is located through the roof or exterior wall to the outer air. A pipe passing through a roof shall extend without interruption through the roof flashing, roof jacket, or roof thimble. [NFPA 54:12.8.4.2]
Single-wall metal pipe shall not originate in an unoccupied attic or concealed space and shall not pass through an attic, inside wall, concealed space, or floor. [NFPA 54:12.8.4.3]
Single-wall metal pipe used for venting an incinerator shall be exposed and readily examinable for its full length and shall have required clearances maintained.
Minimum clearances from single-wall metal pipe to combustible material shall be in accordance with Table 802.7.3.4. Reduced clearances from single-wall metal pipe to combustible material shall be as specified for vent connectors in Table 303.10.1. [NFPA 54:12.8.4.4]

TABLE 802.7.3.4
CLEARANCE FOR CONNECTORS*
[NFPA 54: TABLE 12.8.4.4]
MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL (inches)
APPLIANCE LISTED TYPE B
GAS VENT MATERIAL
LISTED TYPE L
VENT MATERIAL
SINGLE-WALL
METAL PIPE
FACTORY-BUILT
CHIMNEY SECTIONS
Listed appliance with draft hoods and appliance listed for use with Type B gas vents As listed As listed 6 As listed
Residential boilers and furnaces with listed gas
conversion burner and with draft hood
6 6 9 As listed
Residential appliances listed for use with Type L vents Not permitted As listed 9 As listed
Listed gas-fired toilets Not permitted As listed As listed As listed
Unlisted residential appliances with draft hood Not permitted 6 9 As listed
Residential and low-heat appliance other than those
above
Not permitted 9 18 As listed
Medium-heat appliance Not permitted Not permitted 36 As listed
For SI units: 1 inch = 25.4 mm
*  These clearances shall apply unless the installation instructions of a listed appliance or connector specify different clearances, in which case the listed clearances shall apply.
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 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 opening between the draft hood outlet and the thimble, the thimble shall 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, combustible material in the wall shall be removed from the metal pipe to provide the specified clearance from combustible material. Material used to close up such opening shall be noncombustible. [NFPA 54:12.8.4.6]
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 not less than 18 inches (457 mm) above and 6 inches (152 mm) below the roof with the annular space open at the bottom and closed at the top. The thimble shall be sized in accordance with Section 802.7.3.5. [NFPA 54:12.8.4.5]
Single-wall metal piping shall comply with Section 802.7.4.1 through Section 802.7.4.3. [NFPA 54:12.8.5]
A venting system of a 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 803.0.
  2. For a venting system for a single appliance with a draft hood, the areas of the connector and the pipe each shall not be less than the area of the appliance flue collar or draft hood outlet, whichever is smaller. The vent area shall not exceed seven times the draft hood outlet area.
  3. Other approved engineering methods. [NFPA 54:12.8.5(1)]
Where a single-wall metal pipe is used and has a shape other than round, it shall have an effective area equal to the effective area of the round pipe for which it is substituted, and the internal dimension of the pipe shall be not less than 2 inches (51 mm). [NFPA 54:12.8.5(2)]
The vent cap or a roof assembly shall have a venting capacity not less than that of the pipe to which it is attached. [NFPA 54:12.8.5(3)]
Portions of single-wall metal pipe shall be supported for the design and weight of the material employed. [NFPA 54:12.8.6]
Single-wall metal pipe shall comply with the marking provisions of Section 802.6.6. [NFPA 54:12.8.7]
A mechanical draft venting system shall terminate not less than 3 feet (914 mm) above a 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 oflisted outdoor appliances. [NFPA 54:12.9.1]
A mechanical draft venting system of other than direct-vent type shall terminate not less than 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above a door, operable window, or gravity air inlet into a building. The bottom of the vent terminal shall be located not less than 12 inches (305 mm) above finished ground level. [NFPA 54:12.9.2]
The vent terminal of a direct-vent appliance with an input of 10000 Btu/h (3 kW) or less shall be located not less than 6 inches (152 mm) from an air opening into a building, and such an appliance with an input over 10000 Btu/h (3 kW) but not exceeding 50000 Btu/h (14.7 kW) shall be installed with a 9 inch (229 mm) vent termination clearance, and an appliance with an input exceeding 50000 Btu/h (14.7 kW) shall have not less than a 12 inch (305 mm) vent termination clearance. The bottom of the vent terminal and the air intake shall be located not less than 12 inches (305 mm) above finished ground level. [NFPA 54:12.9.3]
Through-the-wall vents for Category II and Category IV appliances and noncategorized condensing appliances shall not terminate over public walkways or over an area where condensate or vapor is capable of creating a nuisance or hazard that is detrimental to the operation of regulators, relief valves, or other equipment. Where local experience indicates that condensate is a problem with Category I and Category III appliances, this provision shall apply.

    Drains for condensate shall be installed in accordance with the appliance and the vent manufacturer's installation instructions. [NFPA 54:12.9.4]
Where vents, including those for direct-vent appliances or combustion air intake pipes, 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. [NFPA 54:12.9.5]
Vent terminals that terminate through an outside wall of a building and discharge flue gases perpendicular to the adjacent wall shall be located not less than 10 feet (3048 mm) horizontally from an operable opening in an adjacent building.

Exception: This shall not apply to vent terminals that are 2 feet (610 mm) or more above or 25 feet (7620 mm) or more below operable openings. [NFPA 54:12.9.6]
Provision shall be made to collect and dispose of condensate from venting systems serving Category II and Category IV appliances and none categorized condensing appliances in accordance with Section 802.8.3. [NFPA 54:12.10.1]
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 Category III appliances in accordance with Section 802.8.3. [NFPA 54:12.10.2]
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. [NFPA 54:12.11.1]
A vent connector shall be made of noncombustible, corrosion resistant material capable of withstanding the vent gas temperature produced by the appliance and of a thickness to withstand physical damage. [NFPA 54:12.11.2.1]
Where the vent connector used for an appliance having a draft hood or a Category I appliance is located in or passes through an unconditioned area, attic or crawl space, that portion of the vent connector shall be listed Type B, Type L, or listed vent material having equivalent insulation qualities.

Exception: Single-wall metal pipe located within the exterior walls of the building and located in an unconditioned area other than an attic or a crawl space having a local 99 percent winter design temperature of 5°F (-15°C) or higher. [NFPA 54:12.11.2.2]
Vent connectors for residential-type appliances shall comply with the following:
  1. Vent connectors for listed appliances having draft hoods, appliances having draft hoods and equipped with listed conversion burners, and Category I appliances that are not installed in attics, crawl spaces, or other unconditioned areas shall be one of the following:

    1. Type B or Type L vent material.
    2. Galvanized sheet steel not less than 0.018 of an inch (0.457 mm) thick.
    3. Aluminum (1100 or 3003 alloy or equivalent) sheet not less than 0.027 of an inch (0.686 mm) thick.
    4. Stainless steel sheet not less than 0.012 of an inch (0.305 mm) thick.
    5. Smooth interior wall metal pipe having resistance to heat and corrosion equal to or exceeding that of Section 802.10.1.2(1)(b), Section 802.10.1.2(1)(c), or Section 802.10.1.2(1)(d) above.
    6. A listed vent connector.
  2. Vent conncctors shall not be covered with insulation.
Exception: Listed insulated vent connectors shall be installed in accordance with the manufacturer's installation instructions. [NFPA 54:12.11.2.3]
A vent connector for a non-residential low-heat appliance shall be a factory-built chimney section or steel pipe having resistance to heat and corrosion equivalent to the galvanized pipe specified in Table 802.10.1.3. Factory-built chimney sections shall be installed in accordance with the chimney manufacturer's installation instructions. [NFPA 54:12.11.2.4]

TABLE 802.10.1.3
MINIMUM THICKNESS FOR GALVANIZED STEEL VENT
CONNECTORS FOR LOW-HEAT APPLIANCES
[NFPA 54: TABLE 12.11.2.4]
DIAMETER OF CONNECTOR
(inches)
MINIMUM THICKNESS
(inches)
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 units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m2
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 802.10.1.4, and shall comply with the following:
  1. A steel vent connector for appliances with a vent gas temperature in excess of 1000°F (538°C) measured at the entrance to the connector shall be lined with medium-duty fire brick or the equivalent.
  2. The lining shall be not less than 212 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 not less than 412 inches (114 mm) thick laid on the 412 inches (114 mm) bed for a vent connector having diameter or greatest cross-sectional dimension exceeding 18 inches (457 mm).
  4. Factory-built chimney sections, where employed, shall be installed in accordance with the chinmey manufacturer's installation instructions. [NFPA 54:12.11.2.5]
TABLE 802.10.1.4
MINIMUM THICKNESS FOR STEEL VENT CONNECTORS
FOR MEDIUM-HEAT APPLIANCES AND COMMERCIAL
AND INDUSTRIAL INCINERATORS
[NFPA 54: TABLE 12.11.2.5]
VENT CONNECTOR SIZE
DIAMETER
(inches)
AREA
(square inches)
MINIMUM THICKNESS
(inches)
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 units: 1 inch = 25.4 mm, 1 square inch = 0.000645 m2
A vent connector for appliances with a single draft hood or for a Category I fan-assisted combustion system appliance shall be sized and installed in accordance with Section 803.0 or other approved engineering methods. [NFPA 54:12.11.3.1]
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 not less than 1 foot (305 mm) rise. [NFPA 54:12.11.3.2]
Where two or more appliances are connected to a common vent or chinmey, each vent connector shall be sized in accordance with Section 803.0 or other approved engineering methods. [NFPA 54:12.11.3.3]

    As an alternative method applicable where 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. [NFPA 54:12.11.3.4]
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 clearance to combustible material and shall be sized in accordance with Section 803.0 or other approved engineering methods. [NFPA 54:12.11.3.5]

    As an alternate method applicable where there are two draft hood-equipped appliances, the effective area of the common vent connector or vent manifold and junction fittings shall be not less than the area of the larger vent connector plus 50 percent of the areas of smaller flue collar outlets. [NFPA 54:12.11.3.6]
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. [NFPA 54:12.11.3.7]
Where two or more openings are provided into one chimney flue or vent, either 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. [NFPA 54:12.11.4.1]
Where two or more vent connectors enter a common 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. [NFPA 54:12.11.4.2]
Vent connectors serving Category I appliances shall not be connected to a portion of a mechanical draft system operating under positive static pressure, such as those serving Category III or Category IV appliances. [NFPA 54:12.11.4.3]
Minimum clearances from vent connectors to combustible material shall comply with Table 802.7.3.4.

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 303.10.1. [NFPA 54:12.11.5]
Joints between sections of connector piping and connections to flue collars or draft hood outlets shall be fastened in accordance with one of the following methods:
  1. By sheet metal screws.
  2. Vent connectors of listed vent material shall be assembled and connected to flue collars or draft hood outlets in accordance with the manufacturer's installation instructions.
  3. Other approved means. [NFPA 54:12.11.6]
A vent connector shall be installed without dips or sags and shall slope upward toward the vent or chimney not less than 14 inch per foot (20.8 mm/m).

Exception: Vent connectors attached to a mechanical draft system installed in accordance with the appliance and draft system manufacturer's installation instructions. [NFPA 54:12.11.7]
The length of vent connectors shall comply with Section 802.10.7.1 or Section 802.10.7.2.
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. [NFPA 54:12.11.8.1]
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. The maximum length of an individual connector for a chimney or vent system serving multiple appliances, from the appliance outlet to the junction with the common vent or another connector, shall be 100 percent of the height of the chimney or vent. [NFPA 54:12.11.8.2]
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. [NFPA 54:12.11.9]
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 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. [NFPA 54:12.11.10]
The entire length of a vent connector shall be readily accessible for inspection, cleaning, and replacement. [NFPA 54:12.11.11]
A vent connector shall not be connected to a chimney flue serving a fireplace unless the fireplace flue opening is permanently sealed. [NFPA 54:12.11.12]
A vent connector shall not pass through a ceiling, floor, or fire-resistance-rated wall. A single-wall metal pipe connector shall not pass through an interior wall.

Exception: Vent connectors made of listed Type B or Type L vent material and serving listed appliances with draft hoods and other appliances listed for use with Type B gas vents that pass through walls or partitions constructed of combustible material shall be installed with not less than the listed clearance to combustible material.
Vent connectors for medium-heat appliances shall not pass through walls or partitions constructed of combustible material. [NFPA 54:12.11.13.2]
The vent connectors for Category II, Category III, and Category IV appliances shall comply with Section 802.4. [NFPA 54:12.12]
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 exceeding 400000 Btu/h (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 listed vented appliances shall be installed without alteration, exactly as furnished and specified by the appliance manufacturer. [NFPA: 54:12.13.2]

    Where a draft hood is not supplied by the appliance manufacturer where one is required, a draft hood shall be installed, be of a listed or approved type, and, in the absence of other instructions, 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. [NFPA: 54:12.13.2.1]

    Where a draft hood of special design is needed or preferable, the installation shall be approved and in accordance with the recommendations of the appliance manufacturer. [NFPA 54:12.13.2.2]
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. [NFPA 54:12.13.3]
Appliances requiring controlled chimney draft shall be permitted to be equipped with listed double-acting barometric draft regulators installed and adjusted in accordance with the manufacturer's installation instructions. [NFPA 54:12.13.4]
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 a difference in pressure between the hood or regulator and the combustion air supply. [NFPA 54:12.13.5]
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 a 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. [NFPA 54:12.13.6]
A draft hood shall be located so that its relief opening is not less than 6 inches (152 mm) from a 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 not be less than that specified on the label. Such clearances shall not be reduced. [NFPA 54:12.13.7]
A manually operated damper shall not be placed in an appliance vent connector. Fixed baffles shall not be classified as manually operated dampers. [NFPA 54:12.14]
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 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. Vent dampers serving listed appliances installed in accordance with Section 803.1 or Section 803.2 or other approved engineering methods.
  5. Approved economizers, heat reclaimers, and recuperators installed in venting systems of appliances not required to be equipped with draft hoods, provided the appliance manufacturer's installation instructions cover the installation of such a device in the venting system and performance in accordance with Section 802.3 and Section 802.3.1 is obtained. [NFPA 54:12.16]
An automatically operated vent damper shall be of a listed type. [NFPA 54:12.15]
Automatically operated vent dampers for oil-fired appliances shall comply with UL 17. The automatic damper control shall comply with UL 378.
Table 803.1.2(1) through Table 803.1.2(6) shall not be used where obstructions arc installed in the venting system. The installation of vents serving listed appliances with vent dampers shall be in accordance with the appliance manufacturer's installation 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 though 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. [NFPA 54:13.1.1]
Where the vent size determined from the tables is smaller than the appliance draft hood outlet or flue collar, the use of the smaller size shall be permitted provided that the installation is in accordance with the following requirements:
  1. The total vent height (H) is not less than 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 dratl hood outlets or flue collars exceeding 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 x maximum table capacity).
  5. The draft hood outlet exceeds 4 inches (102 mm) in diameter. A 3 inch (76 mm) diameter vent shall not be connected to a 4 inch (102 mm) diameter draft hood outlet. This provision shall not apply to fan-assisted appliances. [NFPA 54:13.1.2]
Single-appliance venting configurations with zero lateral lengths in Table 803.1.2(1), Table 803.1.2(2), and Table 803.1.2(5) shall not have elbows in the venting system. Single-appliance venting 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 offsets combined shall not exceed that specified in Table 803.1.2(1) through Table 803.1.2(5). [NFPA 54:13.1.3]

99% Winter Design Temperatures for the Contiguous United States

This map is a necessarily generalized guide to temperatures in the contiguous United States. Temperatures shown for areas such as mountainous regions and large urban centers may not be accurate. The data used to develop this map are from the 1993 ASHRAE Handbook - Fundamentals (Chapter 24, Table 1: Climate Conditions for the United States).

For 99% winter design temperatures in Alaska, consult the ASHRAE Handbook - Fundamentals.

99% winter design temperatures for Hawaii are greater than 37°F.

For SI units: °C = (°F-32)/1.8
FIGURE 803.1.2(6)
RANGE OF WINTER DESIGN TEMPERATURES USED IN ANALYZING EXTERIOR MASONRY CHIMNEYS IN THE UNITED STATES
[NFPA 54: FIGURE F.2.4]

TABLE 803.1.2(1)
TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


TABLE 803.1.2(2)
TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(b)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


TABLE 803.1.2(3)
MASONRY CHIMNEY [NFPA 54: TABLE 13.1(c)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


TABLE 803.1.2(4)
MASONRY CHIMNEY [NFPA 54: TABLE 13.1(d)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


TABLE 803.1.2(5)
SINGLE-WALL METAL PIPE OR TYPE B ASBESTOS-CEMENT VENT [NFPA 54: TABLE 13.1(e)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


TABLE 803.1.2(6)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.1(f)]1, 2
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.

Notes:
1   See Figure 803.1.2(6) for a map showing local 99 percent winter design temperatures in the United States.
2   NA: Not applicable.
Zero lateral (L) shall apply to a straight vertical vent attached to a top outlet draft hood or flue collar. [NFPA 54:13.1.4]
Sea level input ratings shall be used where determining maximum capacity for high-altitude installation. Actual input (derated for altitude) shall be used for determining minimum capacity for high-altitude installation. [NFPA 54:13.1.5]
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 exceed the highest appliance rating input. [NFPA 54:13.1.6]
Listed corrugated metallic chimney liner systems in masonry chimneys shall be sized by using Table 803.1.2(1) or Table 803.1.2(2) for Type B vents, with the maximum capacity reduced by 20 percent (0.80 x maximum capacity) and the minimum capacity as shown in Table 803.1.2(1) or Table 803.1.2(2).

    Corrugated metallic liner systems installed with bends or offsets shall have their maximum capacity further reduced in accordance with Section 803.1.2. 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. [NFPA 54:13.1.7]
Connections between chimney liners and listed double-wall connectors shall be made with listed adapters designed for such purpose. [NFPA 54:13.1.8]
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. [NFPA 54:13.1.9]
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 listed accessory manufacturer's installation instructions. [NFPA 54:13.1.10]
Table 803.1.2(1) through Table 803.1.2(5) shall be used 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. Where vents extend outdoors above the roof more than 5 feet (1524 mm) higher than required by Table 802.6.2, and where vents terminate in accordance with Section 802.6.2(1), the outdoor portion of the vent shall be enclosed as required by this section for vents not considered to be exposed to the outdoors or such venting system shall be engineered. A Type B vent passing through an unventilated enclosure or chase insulated to a value of not less than R-8 shall not be considered to be exposed to the outdoors. Table 803.1.2(3) in combination with Table 803.1.2(6) shall be used for clay-tile-lined exterior masonry chimneys, provided the following requirements are met:
  1. The vent connector is Type B double wall.
  2. The vent connector length is limited to 18 inches/inch (18 mm/mm) of vent connector diameter.
  3. The appliance is draft hood-equipped.
  4. The input rating is less than the maximum capacity given in Table 803.1.2(3).
  5. For a water heater, the outdoor design temperature shall be not less than 5°F (-15°C).
  6. For a space-heating appliance, the input rating exceeds the minimum capacity given by Table 803.1.2(6). [NFPA 54:13.1.11]
Flue lining system for residential and low heat appliance shall be in accordance with Section 803.1.11.1 and Section 803.1.11.2.
Clay flue lining shall be manufactured in accordance with ASTM C315 or other approved standard.
Chimney lining shall be listed in accordance with UL 1777.
Corrugated vent connectors shall not be smaller than the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter. [NFPA 54:13.1.12]
Vent connectors shall not be upsized more than two sizes exceeding the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter. [NFPA 54:13.1.13]
In a single run of vent or vent connector, more than one diameter and type shall be permitted to be used, provided that the sizes and types are permitted by the tables. [NFPA 54:13.1.14]
Interpolation shall be permitted in calculating capacities for vent dimensions that fall between table entries. [NFPA 54:13.1.15]
Extrapolation beyond the table entries shall not be permitted. [NFPA 54:13.1.16]
For vent heights lower than 6 feet (1829 mm) and exceeding vent heights shown in the tables, engineering methods shall be used to calculate vent capacities. [NFPA 54:13.1.17]
Where the actual height of a vent falls between entries in the height column of the applicable table in Table 803.1.2(1) through Table 803.1.2(6), one of the following shall be used:
  1. Interpolation.
  2. The lower appliance input rating shown in the table entries; for FAN MAX and NAT MAX column values and the higher appliance input rating for the FAN MIN column values. [NFPA 54:13.1.18]
Table 803.2(1) through Table 803.2(9) shall not be used where obstructions 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 installation instructions or in accordance with the following:
  1. The maximum capacity of the vent connector shall be determined using the NAT Max column.
  2. The maximum capacity of the vertical vent or chimney shall be determined using the FAN + NAT column where the second appliance is a fan-assisted appliance, or the NAT + NAT column where the second appliance is equipped with a draft hood.
  3. The minimum capacity shall be determined as if the appliance were a fan-assisted appliance, as follows:

    1. The minimum capacity of the vent connector shall be determined using the FAN Min column.
    2. The FAN + FAN column shall be used where the second appliance is a fan-assisted appliance, and the FAN + NAT column shall be used where the second appliance is equipped with a draft hood, to determine whether the vertical vent or chimney configuration is not permitted (NA). Where the vent configuration is NA, the vent configuration shall not be permitted and an alternative venting configuration shall be utilized. [NFPA 54:13.2.1]

TABLE 803.2(1)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(2)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(b)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(3)
MASONRY CHIMNEY [NFPA 54: TABLE 13.2(c)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(4)
MASONRY CHIMNEY [NFPA 54: TABLE 13.2(d)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.


For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable


TABLE 803.2(5)
SINGLE-WALL METAL PIPE OR TYPE B ASBESTOS-CEMENT VENT [NFPA 54:TABlE 13.2(e)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(6)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(f)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(7)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(9)]1, 2
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2, °C = (°F-32)/1.8

Notes:
1   See Figure 803.1.2(6) for a map showing loca1 99 percent winter design temperatures in the Vnited States.
2   NA: Not applicable.



TABLE 803.2(8)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(h)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.



TABLE 803.2(9)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(i)]1, 2
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thelmal units per hour = 0.293 kW, 1 square inch = 0.000645 m2, °C = (°F-32)/1.8

Notes:
1   See Figure 803.1.2(6) for a map showing loca1 99 percent winter design temperatures in the Vnited States.
2   NA: Not applicable.
The maximum vent connector horizontal length shall be 18 inches per inch (18 mm/mm) of connector diameter as shown in Table 803.2.1, or as permitted by Section 803.2.2. [NFPA 54:13.2.2]

TABLE 803.2.1
VENT CONNECTOR MAXIMUM LENGTH
[NFPA 54: TABLE 13.2.2]
CONNECTOR
DIAMETER
(inches)
MAXIMUM CONNECTOR
HORIZONTAL LENGTH
(feet)
3 412
4 6
5 712
6 9
7 1012
8 12
9 1312
10 15
12 18
14 21
16 24
18 27
20 30
22 33
24 36
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
The vent connector shall be routed to the vent utilizing the shortest possible route. Connectors with longer horizontal lengths than those listed in Table 803.2.1 are permitted under the following conditions:
  1. The maximum capacity (FAN Max or NAT Max) of the vent connector shall be reduced 10 percent for each additional multiple of the length listed in Table 803.2.1. For example, the length listed for a 4 inch (l02 mm) connector shall not exceed 6 feet (1829 mm). With a connector length exceeding 6 feet (1829 mm) but not exceeding 12 feet (3658 mm), the maximum capacity shall be reduced by 10 percent (0.90 x maximum vent connector capacity). With a connector length exceeding 12 feet (3658 mm) but not exceeding 18 feet (5486 mm), the maximum capacity shall be reduced by 20 percent (0.80 x maximum vent capacity).
  2. For a connector serving a fan-assisted appliance, the minimum capacity (FAN Min) of the connector shall be determined by referring to the corresponding single appliance table. For Type B double-wall connectors, Table 803.1.2(1) shall be used. For single-wall connectors, Table 803.1.2(2) shall be used. The height (H) and lateral (L) shall be measured according to the procedures for a single-appliance vent, as though the other appliances were not present. [NFPA 54:13.2.3]
Where the vent connectors are combined prior to entering the vertical portion of the common vent to form a common vent manifold, the size of the common vent manifold and the common vent shall be determined by applying a 10 percent reduction (0.90 x maximum common vent capacity) to the common vent capacity part of the common vent tables. The length of the common vent manifold (LM) shall not exceed 18 inches per inch (18 mm/mm) of common vent diameter (D). (See Figure 802.6.4.2) [NFPA 54:13.2.4]
Where the common vertical vent is offset, the maximum capacity of the common vent shall be reduced in accordance with Section 803.2.5, and the horizontal length of the common vent offset shall not exceed 18 inches per inch (18 mm/mm) of common vent diameter (D). Where multiple offsets occur in a common vent, the total horizontal length of offsets combined shall not exceed 18 inches per inch (18 mm/mm) of the common vent diameter. [NFPA 54:13.2.5]
For each elbow up to and including 45 degrees (0.79 rad) in the common vent, the maximum common vent capacity listed in the venting tables shall be reduced by 5 percent. For each elbow exceeding 45 degrees (0.79 rad) up to and including 90 degrees (1.57 rad), the maximum common vent capacity listed in the venting tables shall be reduced by 10 percent. [NFPA 54:13.2.6]
The cross-sectional area of the common vent shall be equal to or exceed the cross-sectional area of the largest connector. [NFPA 54:13.2.8]
Tee and wye fittings connected to a common gas vent shall be considered as part of the common gas vent and constructed of materials consistent with that of the common gas vent. [NFPA 54:13.2.9]
At the point where tee or wye fittings connect to a common gas vent, the opening size of the fitting shall be equal to the size of the common vent. Such fittings shall not be prohibited from having reduced size openings at the point of connection of appliance gas vent connectors. [NFPA 54:13.2.10]
Sea level input ratings shall be used where determining maximum capacity for high-altitude installation. Actual input (derated for altitude) shall be used for determining minimum capacity for high-altitude installation. [NFPA 54:13.2.11]
The connector rise (R) for each appliance connector shall be measured from the draft hood outlet or flue collar to the centerline where the vent gas streams come together. [NFPA 54:13.2.12]
For multiple appliances located on one floor, the total height (H) shall be measured from the highest draft hood outlet or flue collar up to the level of the outlet of the common vent. [NFPA 54:13.2.13]
For multistory installations, the total height (H) for each segment of the system shall be the vertical distance between the highest draft hood outlet or flue collar entering that segment and the centerline of the next higher interconnection tee. (See Figure 803.2.12) [NFPA 54:13.2.14]
FIGURE 803.2.12
MULTISTORY GAS VENT DESIGN PROCEDURE
FOR EACH SEGMENT OF SYSTEM
[NFPA 54: FIGURE F.1(m)]
The size of the lowest connector and of the vertical vent leading to the lowest interconnection of a multistory system shall be in accordance with Table 803.1.2(1) or Table 803.1.2(2) for available total height (H) up to the lowest interconnection. (See Figure 803.2.13) [NFPA 54:13.2.15]
FIGURE 803.2.13
PRINCIPLES OF DESIGN OF MULTISTORY VENTS USING
VENT CONNECTOR AND COMMON VENT DESIGN TABLES
[NFPA 54: FIGURE F.1(n)]
Where used in multistory systems, vertical common vents shall be Type B double-wall and shall be installed with a listed vent cap. [NFPA 54:13.2.16]
Offsets in multistory common vent systems shall be limited to a single offset in each system, and systems with an offset shall comply with the following:
  1. The offset angle shall not exceed 45 degrees (0.79 rad) from vertical.
  2. The horizontal length of the offset shall not exceed 18 inches per inch (18 mm/mm) of common vent diameter of the segment in which the offset is located.
  3. For the segment of the common vertical vent containing the offset, the common vent capacity listed in the common venting tables shall be reduced by 20 percent (0.80 x maximum common vent capacity).
  4. A multistory common vent shall not be reduced in size above the offset. [NFPA 54:13.2.17]
Where two or more appliances are connected to a vertical vent or chimney, the flow area of the largest section of vertical vent or chimney shall not exceed seven times the smallest listed appliance categorized vent areas, flue collar area, or draft hood outlet area unless designed in accordance with approved engineering methods. [NFPA 54:13.2.18]
For appliances with more than one input rate, the minimum vent connector capacity (FAN Min) determined from the tables shall be less than the lowest appliance input rating, and the maximum vent connector capacity (FAN Max or NAT Max) determined from the tables shall exceed the highest appliance input rating. [NFPA 54:13.2.19]
Listed, corrugated metallic chimney liner systems in masonry chimneys shall be sized by using Table 803.2(1) or Table 803.2(2) for Type B vents, with the maximum capacity reduced by 20 percent (0.80 x maximum capacity) and the minimum capacity as shown in Table 803.2(1) or Table 803.2(2). Corrugated metallic liner systems installed with bends or offsets shall have their maximum capacity further reduced in accordance with Section 803.2.5. The 20 percent reduction for corrugated metallic chimney liner systems includes an allowance for one long radius 90 degree (1.57 rad) tum at the bottom of the liner. [NFPA 54:13.2.20]
Table 803.2(1) through Table 803.2(5) shall be used 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 passing through an unventilated enclosure or chase insulated to a value of not less than R-8 shall not be considered to be exposed to the outdoors. Where vents extend outdoors above the roof more than 5 feet (1524 mm) higher than required by Table 802.6.2, and where vents terminate in accordance with Section 802.6.2(1), the outdoor portion of the vent shall be enclosed as required by this section for vents not considered to be exposed to the outdoors or such venting system shall be engineered. Table 803.2(6) through Table 803.2(9) shall be used for clay-tile-lined exterior masonry chimneys, provided the following conditions are met:
  1. The vent connector is Type B double-wall.
  2. Not less than one appliance is draft hood-equipped.
  3. The combined appliance input rating is less than the maximum capacity given by Table 803.2(6) (for NAT+NAT) or Table 803.2(8) (for FAN+NAT).
  4. The input rating of each space-heating appliance exceeds the minimum input rating given by Table 803.2(7) (for NAT+NAT) or Table 803.2(9) (for FAN+NAT).
  5. The vent connector sizing is in accordance with Table 803.2(3). [NFPA 54:13.2.22]
Vent connectors shall not be increased more than two sizes exceeding the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter. Vent connectors for draft hood-equipped appliances shall not be smaller than the draft hood outlet diameter. Where vent connector sizes determined from the tables for fan-assisted appliances are smaller than the flue collar diameter, the use of the smaller sizes shall be permitted provided that the installation is in accordance with the following conditions:
  1. Vent connectors for fan-assisted appliance flue collars 12 inches (305 mm) in diameter or smaller are not reduced by more than one table size [e.g., 12 inches to 10 inches (305 mm to 254 mm) is a one size reduction] and those exceeding 12 inches (305 mm) in diameter are not reduced exceeding two table sizes [e.g., 24 inches to 20 inches (610 mm to 508 mm) is a two-size reduction].
  2. The fan-assisted appliance is common vented with a draft hood-equipped appliance.
  3. The vent connector has a smooth interior wall. [NFPA 54:13.2.24]
Combinations of pipe sizes, single-wall metal pipe, and double-wall metal pipe shall be allowed within a connector run or within the common vent, provided the appropriate tables permit the desired sizes and types of pipe, where they were used for the entire length of the subject connector or vent. Where single-wall and Type B double-wall metal pipes are used for vent connectors within the same venting system, the common vent shall be sized in accordance with Table 803.2(2) or Table 803.2(4). [NFPA 54:13.2.25]
Where a table permits more than one diameter of pipe to be used for a connector or vent, all the permitted sizes shall be permitted to be used. [NFPA 54:13.2.26]
Interpolation shall be permitted in calculating capacities for vent dimensions that fall between table entries. [NFPA 54:13.2.27]
Extrapolation beyond the table entries shall not be permitted. [NFPA 54:13.2.28]
For vent heights lower than 6 feet (1829 mm) and exceeding vent heights shown in the tables, engineering methods shall be used to calculate vent capacities. [NFPA 54:13.2.29]
Where the actual height of a vent falls between entries in the height column of the applicable table in Table 803.2(1) through Table 803.2(9), one of the following shall be used:
  1. Interpolation.
  2. The lower appliance input rating shown in the table entries for FAN MAX and NAT MAX column values; and the higher appliance input rating for the FAN MIN column values. [NFPA 54:13.2.30]
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