Adopts With Amendments:

UMC 2021

Heads up: There are no amended sections in this chapter.
CALIFORNIA MECHANICAL CODE — MATRIX ADOPTION TABLE
CHAPTER 8 — CHIMNEYS AND VENTS
(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
Adopting Agency BSC BSC-CG SFM HCD DSA OSHPD BSCC DPH AGR DWR CEC CA SL SLC
1
2
1-AC
AC
SS
SS/CC
1
1R
2
3
4
5
Adopt Entire Chapter
X
 
X
X
X
   
X
X
X
X
X
X
X
X
               
Adopt Entire Chapter as
amended (amended sections listed below)
                                             
Adopt only those sections
that are listed below
                                             
Chapter/Section                                              
                                               
This state agency does not adopt sections identified with the following symbol:
The Office of the State Fire Marshal's adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
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 1/4 of an inch (6.4 mm) mesh.
Except as permitted in Section 802.2.1 through Section 802.2.7, all 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.
  4. Listed Type 1 clothes dryers exhausted in accordance with Section 504.4.
  5. A single listed booster-type (automatic instantaneous) water heater, when 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, if 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 any 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 any or all of the appliances in Section 802.2.1(5) through Section 802.2.1(11) are installed so the aggregate input rating exceeds 20 Btu/h/ft3 (207 W/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 that the aggregate input rating of the remaining unvented appliances does not exceed 20 Btu/h/ft3 (207 W/m3). [NFPA 54:12.3.2.1]
Where the calculation includes the volume of an adjacent room or space, the room or space in which the appliances are 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 54:12.3.2.2]
The use of ventilating hoods and exhaust systems to vent appliances shall be limited to industrial appliances and appliances installed in commercial applications. [NFPA 54:12.3.3]
The flue gases from industrial-type appliances shall not be required to be vented to the outdoors where such gases are discharged into a large and well-ventilated industrial space. [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 and Section 802.8 and Section 802.8.1. [NFPA 54:12.3.6]
Commercial industrial-type incinerators shall be vented in accordance with NFPA 82. [NFPA 54:12.3.7]
Venting systems shall be designed and constructed to convey all 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 802.15.1. [NFPA 54:12.4.2]
Mechanical draft systems shall be listed in accordance with UL 378 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]
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. [NFPA 54:12.4.3.3]
Vent connectors serving appliances vented by natural draft shall not be connected into any portion of 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 when 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]
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. [NFPA 54:12.4.4.1]
Venting systems shall not extend into or pass through any fabricated air duct or furnace plenum. [NFPA 54:12.4.5.1]
Where a venting system passes through an above-ceiling air space or other nonducted portion of an air-handling system, it shall conform to one of the following requirements:
  1. The venting system shall be a listed special gas vent, other 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 vent system shall be installed such that no fittings or joints between sections are installed in the above-ceiling space.
  3. The venting system shall be installed in a conduit or enclosure with joints between the interior of the enclosure and the ceiling space sealed. [NFPA 54:12.4.5.2]
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]
LOCATION OF REQUIREMENTS
Listed Category I appliances
Listed appliances equipped with draft hood
Appliances listed for use with Type B gas vent
Single-wall metal pipe
Listed chimney lining system for gas
venting
Special gas vent listed for these
appliances
Listed vented wall furnaces
Category II, Category III, and
Category IV appliances
As specified or furnished by
manufacturers of listed appliances
Section 802.4.1 and Section 802.4.3
Incinerators
In accordance with NFPA 82
Appliances that can be converted to use of solid fuel

Unlisted combination gas- and oil-burning appliances

Combination gas- and solid-fuel-burning appliances

Appliances listed for use with chimneys only

Unlisted appliances
Listed combination gas- and oil-burning appliances
Type L vent
Decorative appliances in vented fireplace
Gas-fired toilets
Single-wall metal pipe
Direct-vent appliances
Appliances with integral vents
Where plastic piping is used to vent an appliance, the appliance shall be listed for use with such venting materials and the appliance manufacturer's installation instructions shall identify the specific plastic piping material. The plastic pipe venting materials shall be labeled in accordance with the product standards specified by the appliance manufacturer or shall be listed and labeled in accordance with UL 1738. [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. Plastic pipe venting materials listed and labeled in accordance with UL 1738 shall be installed in accordance with the vent 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 labeled in accordance with UL 1738 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 listed in accordance with UL 103, UL 959, or UL 2561. 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 for solid-fuel room heaters.
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 one of the following:
  1. Approved clay flue lining.
  2. A chimney lining system listed and labeled in accordance with UL 1777.
  3. Other approved material that resists corrosion, erosion, softening, or cracking from vent gases at temperatures up to 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 residential-type or low-heat appliances shall extend at least 3 feet (914 mm) above the highest point where it passes through a roof of a building and at least 2 feet (610 mm) higher than a portion of any building within a horizontal distance of 10 feet (3048 mm). [NFPA 54:12.6.2.1] (See Figure 802.5.4)


(a) Termination 10 ft.(3.0 m) or Less from Ridge, Wall, or Parapet


(b) Termination More Than 10 ft.(3.0 m) from Ridge, Wall, or Parapet

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 medium-heat appliances shall extend at least 10 feet (3048 mm) higher than any portion of any building within 25 feet (7620 mm). [NFPA 54:12.6.2.2]
A chimney shall extend at least 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:
  1. Those listed in Section 803.0.
  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 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 or greater than seven times the smaller 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. [NFPA 54:12.6.3.1]
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 if 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 when an appliance is replaced by an appliance of similar type, input rating, and efficiency, where the chimney complies with Section 802.5.7 through Section 802.5.7.3 and the sizing of the chimney is in accordance with Section 802.5.5. [NFPA 54:12.6.4.2]
Cleanouts shall be examined and where they do not remain tightly closed when not in use, they shall be repaired or replaced. [NFPA 54:12.6.4.3]
When 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 shall be suitable 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 connected through separate openings or 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 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 in accordance with the appliance manufacturer's instructions. [NFPA 54:12.6.5.4]
All 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 installation 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 at least 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]
The installation of gas vents shall meet the following requirements:
  1. Gas vents shall be installed in accordance with the manufacturer's installation instructions.
  2. 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.
  3. 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."
  4. 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 54:12.7.2]
The termination of gas vents shall comply with the following requirements:
  1. A gas vent shall terminate in accordance with one of the following:
    1. Gas vents that are 12 inches (300 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 802.6.1 and Table 802.6.1.
    2. Gas vents that are over 12 inches (300 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.
    3. Industrial appliances as provided in Section 802.2.5.
    4. Direct vent systems as provided in Section 802.2.6.
    5. Appliances with integral vents as provided in Section 802.2.7.
    6. Mechanical draft systems as provided in Section 802.3.3 through Section 802.3.3.5.
    7. Ventilating hoods and exhaust systems as provided in Section 802.3.4.
  2. A Type B or a Type L gas vent shall terminate at least 5 feet (1524 mm) in vertical height above the highest connected appliance draft hood or flue collar.
  3. A Type B-W gas vent shall terminate at least 12 feet (3658 mm) in vertical height above the bottom of the wall furnace.
  4. 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 802.2.6 and Section 802.3.3 through Section 802.3.3.5.
  5. 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.
  6. All gas vents shall extend through the roof flashing, roof jack, or roof thimble and terminate with a listed cap or listed roof assembly.
  7. A gas vent shall terminate at least 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm). [NFPA 54:12.7.3]

FIGURE 802.6.1
TERMINATION LOCATIONS FOR
GAS VENTS WITH LISTED CAPS 12 INCHES OR LESS IN
SIZE NOT LESS THAN 8 FEET FROM A VERTICAL WALL
[NFPA 54: FIGURE 12.7.3]

TABLE 802.6.1
ROOF PITCH HEIGHT
[NFPA 54: TABLE 12.7.3]
ROOF SLOPE
H (minimum) (feet)
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 units: 1 inch = 25.4 mm, 1 foot = 304.8 mm
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 802.6.2.1 through Section 802.6.2.3 and the appliance manufacturer's instructions. [NFPA 54:12.7.4]
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 greater than 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 greater than seven times the smaller draft hood outlet area.
  5. Other approved engineering practices. [NFPA 54:12.7.4.1]
Type B and Type L vents sized in accordance with Section 802.6.2.1(3) or Section 802.6.2.1(4) shall extend in a generally vertical direction with offsets not exceeding 45 degrees except that a vent system having not more than one 60 degree offset shall be permitted. Any angle greater than 45 degrees 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 be greater than 75 percent of the vertical height of the vent. [NFPA 54:12.7.4.2]
The sizing of gas vents for Category II, Category III, and Category IV appliances shall be in accordance with the appliance manufacturer's instructions. The sizing of plastic pipe specified by the appliance manufacturer as a venting material for Category II, III, and IV appliances shall be in accordance with the appliance manufacturers' instructions. [NFPA 54:12.7.4.3]
Chimney venting systems using mechanical draft shall be sized in accordance with approved engineering methods. [NFPA 54:12.7.4.4]
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 54:12.7.5.1]
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 occupiable space. [NFPA 54:12.7.5.2] (See Figure 802.6.3.1)

FIGURE 802.6.3.1
PLAN VIEW OF PRACTICAL SEPARATION METHOD
FOR MULTISTORY GAS VENTING
[NFPA 54: FIGURE A.12.7.5.2]
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 all of the following apply:
  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.
  2. The size of the connector for a segment is determined from the appliance's gas input rate 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 vent segment, and of the interconnection tee at the base of that segment, is based on the total appliance's gas input rate entering that segment and its available total height. [NFPA 54:12.7.5.3]
FIGURE 802.6.3.2
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 54:12.7.6]
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 54:12.7.7]
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 meet the following requirements:
  1. 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.
  2. 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 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 only 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 any unoccupied attic or concealed space and shall not pass through any attic, inside wall, concealed space, or floor. [NFPA 54:12.8.4.3]
Minimum clearances from single-wall metal pipe to combustible material shall be in accordance with Table 802.7.3.3. Reduced clearances from single-wall metal pipe to combustible material shall be as specified for vent connectors. [NFPA 54:12.8.4.4]

TABLE 802.7.3.3
CLEARANCE FOR CONNECTORS*
[NFPA 54: TABLE 12.8.4.4]
MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL (inches)
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
6
Residential boilers and furnaces with listed gas conversion
burner and with draft hood
6
6
9
Residential appliances listed for use with Type L vents
Not permitted
9
Listed gas-fired toilets
Not permitted
Unlisted residential appliances with draft hood
Not permitted
6
9
Residential and low-heat appliance other than those above
Not permitted
9
18
Medium-heat appliance
Not permitted
Not permitted
36
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.
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 a minimum of 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 a minimum of 2 inches (51 mm) larger in diameter than the metal pipe.
  2. For unlisted appliances having draft hoods, the thimble shall be a minimum of 6 inches (152 mm) larger in diameter than the metal pipe.
  3. For residential and low-heat appliances, the thimble shall be a minimum of 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. [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 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 802.7.3.4. [NFPA 54:12.8.4.5]
Single-wall metal piping shall comply with the following requirements:
  1.  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 be greater than seven times the draft hood outlet area.
    3. Other approved engineering methods.
  2. Where a single-wall metal pipe is used and has a shape other than round, it shall have an equivalent effective area equal to the effective area of the round pipe for which it is substituted and the minimum internal dimension of the pipe shall be 2 inches (51 mm).
  3. 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]
All 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 802.6.5. [NFPA 54:12.8.7]
A mechanical draft venting system shall terminate at least 3 feet (914 mm) above any forced air inlet located within 10 feet (3048 mm). (See Figure 802.8)

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. [NFPA 54:12.9.1]


FIGURE 802.8
EXIT TERMINALS OF MECHANICAL DRAFT AND DIRECT VENT VENTING SYSTEMS
[NFPA 54: FIGURE A.12.9]
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 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. [NFPA 54:12.9.2]
The clearances for through-the-wall direct vent terminals shall be in accordance with Table 802.8.2. 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]

TABLE 802.8.2
THROUGH-THE-WALL DIRECT VENT TERMINATION CLEARANCES
[NFPA 54: TABLE 12.9.3]
DIRECT VENT APPLIANCE INPUT RATING
THROUGH THE WALL VENT TERMINAL CLEARANCE FROM ANY AIR OPENING INTO A BUILDING (inches)
10 000 Btu/h and less
6
Greater than 10 000 Btu/h and not exceeding 50 000 Btu/h
9
Greater than 50 000 Btu/h and not exceeding 150 000 Btu/h
12
> 150 000 Btu/h
In accordance with the appliance manufacturer's instructions and in no case less than the clearances specified in Section 802.8.1.
For SI Units: 1 inch = 25.4 mm, 1000 British thermal units per hour = 0.293 kW
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 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 Category III appliances, this provision shall also 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 systems for Category IV appliances 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 noncategorized 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 sufficient 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 greater than that of Section 802.10.1.2(1)(b), Section 802.10.1.2(1)(c), or Section 802.10.1.2(1)(d).
    6. A listed vent connector.
  2. Vent connectors 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 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 802.10.1.3. Factory-built chimney sections shall be joined together in accordance with the chimney manufacturer's 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 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 an appliance 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 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 inches (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. [NFPA 54:12.11.2.5]
TABLE 802.10.1.4
MINIMUM THICKNESS FOR STEEL VENT CONNECTORS FOR MEDIUM-HEAT APPLIANCES
[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 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 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 alternative 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. [NFPA 54:12.11.3.2]
Where two or more appliances are connected to a common vent or chimney, 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 only where 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. [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 sized in accordance with Section 803.0 or other approved engineering methods. [NFPA 54:12.11.3.5]

     As an alternative 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. [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 of the following shall apply:
  1. The openings shall be at different levels.
  2. The connectors shall be attached to the vertical portion of the chimney or vent at an angle of 45 degrees 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 any 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 be in accordance with Table 802.7.3.3.

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. Sheet metal screws.
  2. Vent connectors of listed vent material assembled and connected to flue collars or draft hood outlets in accordance with the manufacturer's instructions.
  3. Other approved means. [NFPA 54:12.11.6]
A vent connector shall be installed without any dips or sags and shall slope upward toward the vent or chimney at least 1/4 inch per foot (20.8 mm/m).

Exception: Vent connectors attached to a mechanical draft system installed in accordance with appliance and the draft system manufacturers' 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 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. [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 be in accordance with Section 802.4 through Section 802.4.3. [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 greater than 400 000 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. [NFPA 54:12.13.1]
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. [NFPA 54:12.13.2]

     If 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 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 any 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 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. [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 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 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 any 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 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.
Venting Table 803.1.2(1) through Table 803.1.2(6) 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 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 complies with all of the following requirements:
  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 x maximum table capacity).
  5. The draft hood outlet is greater than 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 (0) 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 elbows. For each additional elbow up to and including 45 degrees, the maximum capacity listed in the venting tables shall be reduced by 5 percent. For each additional elbow greater than 45 degrees up to and including 90 degrees, 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 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 are not necessarily accurate. The climate data used to develop this map are from the ASHRAE Handbook — Fundamentals (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)]*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
CATEGORY I
APPLIANCE VENT CONNECTION:
CONNECTED DIRECTLY TO VENT
VENT DIAMETER — D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6
0
0
78
46
0
152
86
0
251
141
0
375
205
0
524
285
2
13
51
36
18
97
67
27
157
105
32
232
157
44
321
217
4
21
49
34
30
94
64
39
153
103
50
227
153
66
316
211
6
25
46
32
36
91
61
47
149
100
59
223
149
78
310
205
8
0
0
84
50
0
165
94
0
276
155
0
415
235
0
583
320
2
12
57
40
16
109
75
25
178
120
28
263
180
42
365
247
5
23
53
38
32
103
71
42
171
115
53
255
173
70
356
237
8
28
49
35
39
98
66
51
164
109
64
247
165
84
347
227
10
0
0
88
53
0
175
100
0
295
166
0
447
255
0
631
345
2
12
61
42
17
118
81
23
194
129
26
289
195
40
402
273
5
23
57
40
32
113
77
41
187
124
52
280
188
68
392
263
10
30
51
36
41
104
70
54
176
115
67
267
175
88
376
245
15
0
0
94
58
0
191
112
0
327
187
0
502
285
0
716
390
2
11
69
48
15
136
93
20
226
150
22
339
225
38
475
316
5
22
65
45
30
130
87
39
219
142
49
330
217
64
463
300
10
29
59
41
40
121
82
51
206
135
64
315
208
84
445
288
15
35
53
37
48
112
76
61
195
128
76
301
198
98
429
275
20
0
0
97
61
0
202
119
0
349
202
0
540
307
0
776
430
2
10
75
51
14
149
100
18
250
166
20
377
249
33
531
346
5
21
71
48
29
143
96
38
242
160
47
367
241
62
519
337
10
28
64
44
38
133
89
50
229
150
62
351
228
81
499
321
15
34
58
40
46
124
84
59
217
142
73
337
217
94
481
308
20
48
52
35
55
116
78
69
206
134
84
322
206
107
464
295
30
0
0
100
64
0
213
128
0
374
220
0
587
336
0
853
475
2
9
81
56
13
166
112
14
283
185
18
432
280
27
613
394
5
21
77
54
28
160
108
36
275
176
45
421
273
58
600
385
10
27
70
50
37
150
102
48
262
171
59
405
261
77
580
371
15
33
64
NA
44
141
96
57
249
163
70
389
249
90
560
357
20
56
58
NA
53
132
90
66
237
154
80
374
237
102
542
343
30
NA
NA
NA
73
113
NA
88
214
NA
104
346
219
131
507
321
50
0
0
101
67
0
216
134
0
397
232
0
633
363
0
932
518
2
8
86
61
11
183
122
14
320
206
15
497
314
22
715
445
5
20
82
NA
27
177
119
35
312
200
43
487
308
55
702
438
10
26
76
NA
35
168
114
45
299
190
56
471
298
73
681
426
15
59
70
NA
42
158
NA
54
287
180
66
455
288
85
662
413
20
NA
NA
NA
50
149
NA
63
275
169
76
440
278
97
642
401
30
NA
NA
NA
69
131
NA
84
250
NA
99
410
259
123
605
376
100
0
NA
NA
NA
0
218
NA
0
407
NA
0
665
400
0
997
560
2
NA
NA
NA
10
194
NA
12
354
NA
13
566
375
18
831
510
5
NA
NA
NA
26
189
NA
33
347
NA
40
557
369
52
820
504
10
NA
NA
NA
33
182
NA
43
335
NA
53
542
361
68
801
493
15
NA
NA
NA
40
174
NA
50
321
NA
62
528
353
80
782
482
20
NA
NA
NA
47
166
NA
59
311
NA
71
513
344
90
763
471
30
NA
NA
NA
NA
NA
NA
78
290
NA
92
483
NA
115
726
449
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
147
428
NA
180
651
405
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(1)
TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)] (continued)
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
CONNECTED DIRECTLY TO VENT
VENT DIAMETER — D (inch)
8 9 10 12 14
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6
0 0 698 370 0 897 470 0 1121 570 0 1645 850 0 2267 1170
2 53 425 285 63 543 370 75 675 455 103 982 650 138 1346 890
4 79 419 279 93 536 362 110 668 445 147 975 640 191 1338 880
6 93 413 273 110 530 354 128 661 435 171 967 630 219 1330 870
8 0 0 780 415 0 1006 537 0 1261 660 0 1858 970 0 2571 1320
2 50 483 322 60 619 418 71 770 515 98 1124 745 130 1543 1020
5 83 473 313 99 607 407 115 758 503 154 1110 733 199 1528 1010
8 99 463 303 117 596 396 137 746 490 180 1097 720 231 1514 1000
10 0 0 847 450 0 1096 585 0 1377 720 0 2036 1060 0 2825 1450
2 48 533 355 57 684 457 68 852 560 93 1244 850 124 1713 1130
5 81 522 346 95 671 446 112 839 547 149 1229 829 192 1696 1105
10 104 504 330 122 651 427 142 817 525 187 1204 795 238 1669 1080
15 0 0 970 525 0 1263 682 0 1596 840 0 2380 1240 0 3323 1720
2 45 633 414 53 815 544 63 1019 675 86 1495 985 114 2062 1350
5 76 620 403 90 800 529 105 1003 660 140 1476 967 182 2041 1327
10 99 600 386 116 777 507 135 977 635 177 1446 936 227 2009 1289
15 115 580 373 134 755 491 155 953 610 202 1418 905 257 1976 1250
20 0 0 1057 575 0 1384 752 0 1756 930 0 2637 1350 0 3701 1900
2 41 711 470 50 917 612 59 1150 755 81 1694 1100 107 2343 1520
5 73 697 460 86 902 599 101 1133 738 135 1674 1079 174 2320 1498
10 95 675 443 112 877 576 130 1105 710 172 1641 1045 220 2282 1460
15 111 654 427 129 853 557 150 1078 688 195 1609 1018 248 2245 1425
20 125 634 410 145 830 537 167 1052 665 217 1578 990 273 2210 1390
30 0 0 1173 650 0 1548 855 0 1977 1060 0 3004 1550 0 4252 2170
2 33 826 535 42 1072 700 54 1351 865 74 2004 1310 98 2786 1800
5 69 811 524 82 1055 688 96 1332 851 127 1981 1289 164 2759 1775
10 91 788 507 107 1028 668 125 1301 829 164 1944 1254 209 2716 1733
15 105 765 490 124 1002 648 143 1272 807 187 1908 1220 237 2674 1692
20 119 743 473 139 977 628 160 1243 784 207 1873 1185 260 2633 1650
30 149 702 444 171 929 594 195 1189 745 246 1807 1130 305 2555 1585
50 0 0 1297 708 0 1730 952 0 2231 1195 0 3441 1825 0 4934 2550
2 26 975 615 33 1276 813 41 1620 1010 66 2431 1513 86 3409 2125
5 65 960 605 77 1259 798 90 1600 996 118 2406 1495 151 3380 2102
10 86 935 589 101 1230 773 118 1567 972 154 2366 1466 196 3332 2064
15 100 911 572 117 1203 747 136 1536 948 177 2327 1437 222 3285 2026
20 113 888 556 131 1176 722 151 1505 924 195 2288 1408 244 3239 1987
30 141 844 522 161 1125 670 183 1446 876 232 2214 1349 287 3150 1910
100 0 0 1411 770 0 1908 1040 0 2491 1310 0 3925 2050 0 5729 2950
2 21 1155 700 25 1536 935 30 1975 1170 44 3027 1820 72 4313 2550
5 60 1141 692 71 1519 926 82 1955 1159 107 3002 1803 136 4282 2531
10 80 1118 679 94 1492 910 108 1923 1142 142 2961 1775 180 4231 2500
15 93 1095 666 109 1465 895 126 1892 1124 163 2920 1747 206 4182 2469
20 105 1073 653 122 1438 880 141 1861 1107 181 2880 1719 226 4133 2438
30 131 1029 627 149 1387 849 170 1802 1071 215 2803 1663 265 4037 2375
50 197 944 575 217 1288 787 241 1688 1000 292 2657 1550 350 3856 2250
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
TABLE 803.1.2(1)
TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(a)] (continued)
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
CONNECTED DIRECTLY TO VENT
VENT DIAMETER — D (inch)
16 18 20 22 24
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6 0 0 2983 1530 0 3802 1960 0 4721 2430 0 5737 2950 0 6853 3520
2 178 1769 1170 225 2250 1480 296 2782 1850 360 3377 2220 426 4030 2670
4 242 1761 1160 300 2242 1475 390 2774 1835 469 3370 2215 555 4023 2660
6 276 1753 1150 341 2235 1470 437 2767 1820 523 3363 2210 618 4017 2650
8 0 0 3399 1740 0 4333 2220 0 5387 2750 0 6555 3360 0 7838 4010
2 168 2030 1340 212 2584 1700 278 3196 2110 336 3882 2560 401 4634 3050
5 251 2013 1330 311 2563 1685 398 3180 2090 476 3863 2545 562 4612 3040
8 289 2000 1320 354 2552 1670 450 3163 2070 537 3850 2530 630 4602 3030
10 0 0 3742 1925 0 4782 2450 0 5955 3050 0 7254 3710 0 8682 4450
2 161 2256 1480 202 2868 1890 264 3556 2340 319 4322 2840 378 5153 3390
5 243 2238 1461 300 2849 1871 382 3536 2318 458 4301 2818 540 5132 3371
10 298 2209 1430 364 2818 1840 459 3504 2280 546 4268 2780 641 5099 3340
15 0 0 4423 2270 0 5678 2900 0 7099 3620 0 8665 4410 0 10 393 5300
2 147 2719 1770 186 3467 2260 239 4304 2800 290 5232 3410 346 6251 4080
5 229 2696 1748 283 3442 2235 355 4278 2777 426 5204 3385 501 6222 4057
10 283 2659 1712 346 3402 2193 432 4234 2739 510 5159 3343 599 6175 4019
15 318 2623 1675 385 3363 2150 479 4192 2700 564 5115 3300 665 6129 3980
20 0 0 4948 2520 0 6376 3250 0 7988 4060 0 9785 4980 0 11 753 6000
2 139 3097 2000 175 3955 2570 220 4916 3200 269 5983 3910 321 7154 4700
5 219 3071 1978 270 3926 2544 337 4885 3174 403 5950 3880 475 7119 4662
10 273 3029 1940 334 3880 2500 413 4835 3130 489 5896 3830 573 7063 4600
15 306 2988 1910 372 3835 2465 459 4786 3090 541 5844 3795 631 7007 4575
20 335 2948 1880 404 3791 2430 495 4737 3050 585 5792 3760 689 6953 4550
30 0 0 5725 2920 0 7420 3770 0 9341 4750 0 11 483 5850 0 13 848 7060
2 127 3696 2380 159 4734 3050 199 5900 3810 241 7194 4650 285 8617 5600
5 206 3666 2350 252 4701 3020 312 5863 3783 373 7155 4622 439 8574 5552
10 259 3617 2300 316 4647 2970 386 5803 3739 456 7090 4574 535 8505 5471
15 292 3570 2250 354 4594 2920 431 5744 3695 507 7026 4527 590 8437 5391
20 319 3523 2200 384 4542 2870 467 5686 3650 548 6964 4480 639 8370 5310
30 369 3433 2130 440 4442 2785 540 5574 3565 635 6842 4375 739 8239 5225
50 0 0 6711 3440 0 8774 4460 0 11 129 5635 0 13 767 6940 0 16 694 8430
2 113 4554 2840 141 5864 3670 171 7339 4630 209 8980 5695 251 10 788 6860
5 191 4520 2813 234 5826 3639 283 7295 4597 336 8933 5654 394 10 737 6818
10 243 4464 2767 295 5763 3585 355 7224 4542 419 8855 5585 491 10 652 6749
15 274 4409 2721 330 5701 3534 396 7155 4511 465 8779 5546 542 10 570 6710
20 300 4356 2675 361 5641 3481 433 7086 4479 506 8704 5506 586 10 488 6670
30 347 4253 2631 412 5523 3431 494 6953 4421 577 8557 5444 672 10 328 6603
100 0 0 7914 4050 0 10 485 5300 0 13 454 6700 0 16 817 8600 0 20 578 10 300
2 95 5834 3500 120 7591 4600 138 9577 5800 169 11 803 7200 204 14 264 8800
5 172 5797 3475 208 7548 4566 245 9528 5769 293 11 748 7162 341 14 204 8756
10 223 5737 3434 268 7478 4509 318 9447 5717 374 11 658 7100 436 14 105 8683
15 252 5678 3392 304 7409 4451 358 9367 5665 418 11 569 7037 487 14 007 8610
20 277 5619 3351 330 7341 4394 387 9289 5613 452 11 482 6975 523 13 910 8537
30 319 5505 3267 378 7209 4279 446 9136 5509 514 11 310 6850 592 13 720 8391
50 415 5289 3100 486 6956 4050 572 8841 5300 659 10 979 6600 752 13 354 8100
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

TABLE 803.1.2(2)
TYPE B DOUBLE-WALL GAS VENT [NFPA 54: TABLE 13.1(b)]*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
CATEGORY I
APPLIANCE VENT CONNECTION:
SINGLE-WALL METAL CONNECTOR
VENT DIAMETER — D (inch)
3
4
5
6
7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6
0
38
77
45
59
151
85
85
249
140
126
373
204
165
522
284
2
39
51
36
60
96
66
85
156
104
123
231
156
159
320
213
4
NA
NA
33
74
92
63
102
152
102
146
225
152
187
313
208
6
NA
NA
31
83
89
60
114
147
99
163
220
148
207
307
203
8
0
37
83
50
58
164
93
83
273
154
123
412
234
161
580
319
2
39
56
39
59
108
75
83
176
119
121
261
179
155
363
246
5
NA
NA
37
77
102
69
107
168
114
151
252
171
193
352
235
8
NA
NA
33
90
95
64
122
161
107
175
243
163
223
342
225
10
0
37
87
53
57
174
99
82
293
165
120
444
254
158
628
344
2
39
61
41
59
117
80
82
193
128
119
287
194
153
400
272
5
52
56
39
76
111
76
105
185
122
148
277
186
190
388
261
10
NA
NA
34
97
100
68
132
171
112
188
261
171
237
369
241
15
0
36
93
57
56
190
111
80
325
186
116
499
283
153
713
388
2
38
69
47
57
136
93
80
225
149
115
337
224
148
473
314
5
51
63
44
75
128
86
102
216
140
144
326
217
182
459
298
10
NA
NA
39
95
116
79
128
201
131
182
308
203
228
438
284
15
NA
NA
NA
NA
NA
72
158
186
124
220
290
192
272
418
269
20
0
35
96
60
54
200
118
78
346
201
114
537
306
149
772
428
2
37
74
50
56
148
99
78
248
165
113
375
248
144
528
344
5
50
68
47
73
140
94
100
239
158
141
363
239
178
514
334
10
NA
NA
41
93
129
86
125
223
146
177
344
224
222
491
316
15
NA
NA
NA
NA
NA
80
155
208
136
216
325
210
264
469
301
20
NA
NA
NA
NA
NA
NA
186
192
126
254
306
196
309
448
285
30
0
34
99
63
53
211
127
76
372
219
110
584
334
144
849
472
2
37
80
56
55
164
111
76
281
183
109
429
279
139
610
392
5
49
74
52
72
157
106
98
271
173
136
417
271
171
595
382
10
NA
NA
NA
91
144
98
122
255
168
171
397
257
213
570
367
15
NA
NA
NA
115
131
NA
151
239
157
208
377
242
255
547
349
20
NA
NA
NA
NA
NA
NA
181
223
NA
246
357
228
298
524
333
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
389
477
305
50
0
33
99
66
51
213
133
73
394
230
105
629
361
138
928
515
2
36
84
61
53
181
121
73
318
205
104
495
312
133
712
443
5
48
80
NA
70
174
117
94
308
198
131
482
305
164
696
435
10
NA
NA
NA
89
160
NA
118
292
186
162
461
292
203
671
420
15
NA
NA
NA
112
148
NA
145
275
174
199
441
280
244
646
405
20
NA
NA
NA
NA
NA
NA
176
257
NA
236
420
267
285
622
389
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
315
376
NA
373
573
NA
100
0
NA
NA
NA
49
214
NA
69
403
NA
100
659
395
131
991
555
2
NA
NA
NA
51
192
NA
70
351
NA
98
563
373
125
828
508
5
NA
NA
NA
67
186
NA
90
342
NA
125
551
366
156
813
501
10
NA
NA
NA
85
175
NA
113
324
NA
153
532
354
191
789
486
15
NA
NA
NA
132
162
NA
138
310
NA
188
511
343
230
764
473
20
NA
NA
NA
NA
NA
NA
168
295
NA
224
487
NA
270
739
458
30
NA
NA
NA
NA
NA
NA
231
264
NA
301
448
NA
355
685
NA
50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
540
584
NA
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)] (continued)*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
SINGLE-WALL METAL CONNECTOR
VENT DIAMETER — D (inch)
8 9 10 12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
FAN NAT FAN NAT FAN NAT FAN NAT
Min Max Max Min Max Max Min Max Max Min Max Max
6 0 211 695 369 267 894 469 371 1118 569 537 1639 849
2 201 423 284 251 541 368 347 673 453 498 979 648
4 237 416 277 295 533 360 409 664 443 584 971 638
6 263 409 271 327 526 352 449 656 433 638 962 627
8 0 206 777 414 258 1002 536 360 1257 658 521 1852 967
2 197 482 321 246 617 417 339 768 513 486 1120 743
5 245 470 311 305 604 404 418 754 500 598 1104 730
8 280 458 300 344 591 392 470 740 486 665 1089 715
10 0 202 844 449 253 1093 584 351 1373 718 507 2031 1057
2 193 531 354 242 681 456 332 849 559 475 1242 848
5 241 518 344 299 667 443 409 834 544 584 1224 825
10 296 497 325 363 643 423 492 808 520 688 1194 788
15 0 195 966 523 244 1259 681 336 1591 838 488 2374 1237
2 187 631 413 232 812 543 319 1015 673 457 1491 983
5 231 616 400 287 795 526 392 997 657 562 1469 963
10 284 592 381 349 768 501 470 966 628 664 1433 928
15 334 568 367 404 742 484 540 937 601 750 1399 894
20 0 190 1053 573 238 1379 750 326 1751 927 473 2631 1346
2 182 708 468 227 914 611 309 1146 754 443 1689 1098
5 224 692 457 279 896 596 381 1126 734 547 1665 1074
10 277 666 437 339 866 570 457 1092 702 646 1626 1037
15 325 640 419 393 838 549 526 1060 677 730 1587 1005
20 374 616 400 448 810 526 592 1028 651 808 1550 973
30 0 184 1168 647 229 1542 852 312 1971 1056 454 2996 1545
2 175 823 533 219 1069 698 296 1346 863 424 1999 1308
5 215 806 521 269 1049 684 366 1324 846 524 1971 1283
10 265 777 501 327 1017 662 440 1287 821 620 1927 1243
15 312 750 481 379 985 638 507 1251 794 702 1884 1205
20 360 723 461 433 955 615 570 1216 768 780 1841 1166
30 461 670 426 541 895 574 704 1147 720 937 1759 1101
50 0 176 1292 704 220 1724 948 295 2223 1189 428 3432 1818
2 168 971 613 209 1273 811 280 1615 1007 401 2426 1509
5 204 953 602 257 1252 795 347 1591 991 496 2396 1490
10 253 923 583 313 1217 765 418 1551 963 589 2347 1455
15 299 894 562 363 1183 736 481 1512 934 668 2299 1421
20 345 866 543 415 1150 708 544 1473 906 741 2251 1387
30 442 809 502 521 1086 649 674 1399 848 892 2159 1318
100 0 166 1404 765 207 1900 1033 273 2479 1300 395 3912 2042
2 158 1152 698 196 1532 933 259 1970 1168 371 3021 1817
5 194 1134 688 240 1511 921 322 1945 1153 460 2990 1796
10 238 1104 672 293 1477 902 389 1905 1133 547 2938 1763
15 281 1075 656 342 1443 884 447 1865 1110 618 2888 1730
20 325 1046 639 391 1410 864 507 1825 1087 690 2838 1696
30 418 988 NA 491 1343 824 631 1747 1041 834 2739 1627
50 617 866 NA 711 1205 NA 895 1591 NA 1138 2547 1489
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)]*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
TYPE B DOUBLE-WALL CONNECTOR
TYPE B DOUBLE-WALL CONNECTOR DIAMETER — D (inch)
TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM
3 4 5 6 7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6 2 NA NA 28 NA NA 52 NA NA 86 NA NA 130 NA NA 180
5 NA NA 25 NA NA 49 NA NA 82 NA NA 117 NA NA 165
8 2 NA NA 29 NA NA 55 NA NA 93 NA NA 145 NA NA 198
5 NA NA 26 NA NA 52 NA NA 88 NA NA 134 NA NA 183
8 NA NA 24 NA NA 48 NA NA 83 NA NA 127 NA NA 175
10 2 NA NA 31 NA NA 61 NA NA 103 NA NA 162 NA NA 221
5 NA NA 28 NA NA 57 NA NA 96 NA NA 148 NA NA 204
10 NA NA 25 NA NA 50 NA NA 87 NA NA 139 NA NA 191
15 2 NA NA 35 NA NA 67 NA NA 114 NA NA 179 53 475 250
5 NA NA 35 NA NA 62 NA NA 107 NA NA 164 NA NA 231
10 NA NA 28 NA NA 55 NA NA 97 NA NA 153 NA NA 216
15 NA NA NA NA NA 48 NA NA 89 NA NA 141 NA NA 201
20 2 NA NA 38 NA NA 74 NA NA 124 NA NA 201 51 522 274
5 NA NA 36 NA NA 68 NA NA 116 NA NA 184 80 503 254
10 NA NA NA NA NA 60 NA NA 107 NA NA 172 NA NA 237
15 NA NA NA NA NA NA NA NA 97 NA NA 159 NA NA 220
20 NA NA NA NA NA NA NA NA 83 NA NA 148 NA NA 206
30 2 NA NA 41 NA NA 82 NA NA 137 NA NA 216 47 581 303
5 NA NA NA NA NA 76 NA NA 128 NA NA 198 75 561 281
10 NA NA NA NA NA 67 NA NA 115 NA NA 184 NA NA 263
15 NA NA NA NA NA NA NA NA 107 NA NA 171 NA NA 243
20 NA NA NA NA NA NA NA NA 91 NA NA 159 NA NA 227
30 NA NA NA NA NA NA NA NA NA NA NA NA NA NA 188
50 2 NA NA NA NA NA 92 NA NA 161 NA NA 251 NA NA 351
5 NA NA NA NA NA NA NA NA 151 NA NA 230 NA NA 323
10 NA NA NA NA NA NA NA NA 138 NA NA 215 NA NA 304
15 NA NA NA NA NA NA NA NA 127 NA NA 199 NA NA 282
20 NA NA NA NA NA NA NA NA NA NA NA 185 NA NA 264
30 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
Minimum
internal area of
chimney
(square inches)
12 19 28 38 50
Maximum
internal area of
chimney
(square inches)
Seven times the listed appliance categorized vent area, flue collar area, or draft hood outlet areas.
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)] (continued)*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
TYPE B DOUBLE-WALL CONNECTOR
TYPE B DOUBLE-WALL CONNECTOR DIAMETER — D (inch)
TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM
8 9 10 12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
FAN NAT FAN NAT FAN NAT FAN NAT
Min Max Max Min Max Max Min Max Max Min Max Max
6 2 NA NA 247 NA NA 320 NA NA 401 NA NA 581
5 NA NA 231 NA NA 298 NA NA 376 NA NA 561
8 2 NA NA 266 84 590 350 100 728 446 139 1024 651
5 NA NA 247 NA NA 328 149 711 423 201 1007 640
8 NA NA 239 NA NA 318 173 695 410 231 990 623
10 2 68 519 298 82 655 388 98 810 491 136 1144 724
5 NA NA 277 124 638 365 146 791 466 196 1124 712
10 NA NA 263 155 610 347 182 762 444 240 1093 668
15 2 64 613 336 77 779 441 92 968 562 127 1376 841
5 99 594 313 118 759 416 139 946 533 186 1352 828
10 126 565 296 148 727 394 173 912 567 229 1315 777
15 NA NA 281 171 698 375 198 880 485 259 1280 742
20 2 61 678 375 73 867 491 87 1083 627 121 1548 953
5 95 658 350 113 845 463 133 1059 597 179 1523 933
10 122 627 332 143 811 440 167 1022 566 221 1482 879
15 NA NA 314 165 780 418 191 987 541 251 1443 840
20 NA NA 296 186 750 397 214 955 513 277 1406 807
30 2 57 762 421 68 985 558 81 1240 717 111 1793 1112
5 90 741 393 106 962 526 125 1216 683 169 1766 1094
10 115 709 373 135 927 500 158 1176 648 210 1721 1025
15 NA NA 353 156 893 476 181 1139 621 239 1679 981
20 NA NA 332 176 860 450 203 1103 592 264 1638 940
30 NA NA 288 NA NA 416 249 1035 555 318 1560 877
50 2 51 840 477 61 1106 633 72 1413 812 99 2080 1243
5 83 819 445 98 1083 596 116 1387 774 155 2052 1225
10 NA NA 424 126 1047 567 147 1347 733 195 2006 1147
15 NA NA 400 146 1010 539 170 1307 702 222 1961 1099
20 NA NA 376 165 977 511 190 1269 669 246 1916 1050
30 NA NA 327 NA NA 468 233 1196 623 295 1832 984
Minimum
internal area of
chimney
(square inches)
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 areas.
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)]*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
SINGLE-WALL METAL CONNECTOR
SINGLE-WALL METAL CONNECTOR DIAMETER — D (inch)
TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM
3 4 5 6 7
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
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
6 2 NA NA 28 NA NA 52 NA NA 86 NA NA 130 NA NA 180
5 NA NA 25 NA NA 48 NA NA 81 NA NA 116 NA NA 164
8 2 NA NA 29 NA NA 55 NA NA 93 NA NA 145 NA NA 197
5 NA NA 26 NA NA 51 NA NA 87 NA NA 133 NA NA 182
8 NA NA 23 NA NA 47 NA NA 82 NA NA 126 NA NA 174
10 2 NA NA 31 NA NA 61 NA NA 102 NA NA 161 NA NA 220
5 NA NA 28 NA NA 56 NA NA 95 NA NA 147 NA NA 203
10 NA NA 24 NA NA 49 NA NA 86 NA NA 137 NA NA 189
15 2 NA NA 35 NA NA 67 NA NA 113 NA NA 178 166 473 249
5 NA NA 32 NA NA 61 NA NA 106 NA NA 163 NA NA 230
10 NA NA 27 NA NA 54 NA NA 96 NA NA 151 NA NA 214
15 NA NA NA NA NA 46 NA NA 87 NA NA 138 NA NA 198
20 2 NA NA 38 NA NA 73 NA NA 123 NA NA 200 163 520 273
5 NA NA 35 NA NA 67 NA NA 115 NA NA 183 NA NA 252
10 NA NA NA NA NA 59 NA NA 105 NA NA 170 NA NA 235
15 NA NA NA NA NA NA NA NA 95 NA NA 156 NA NA 217
20 NA NA NA NA NA NA NA NA 80 NA NA 144 NA NA 202
30 2 NA NA 41 NA NA 81 NA NA 136 NA NA 215 158 578 302
5 NA NA NA NA NA 75 NA NA 127 NA NA 196 NA NA 279
10 NA NA NA NA NA 66 NA NA 113 NA NA 182 NA NA 260
15 NA NA NA NA NA NA NA NA 105 NA NA 168 NA NA 240
20 NA NA NA NA NA NA NA NA 88 NA NA 155 NA NA 223
30 NA NA NA NA NA NA NA NA NA NA NA NA NA NA 182
50 2 NA NA NA NA NA 91 NA NA 160 NA NA 250 NA NA 350
5 NA NA NA NA NA NA NA NA 149 NA NA 228 NA NA 321
10 NA NA NA NA NA NA NA NA 136 NA NA 212 NA NA 301
15 NA NA NA NA NA NA NA NA 124 NA NA 195 NA NA 278
20 NA NA NA NA NA NA NA NA NA NA NA 180 NA NA 258
30 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
Minimum
internal area of
chimney
(square inches)
12 19 28 38 50
Maximum
internal area of
chimney
(square inches)
Seven times the listed appliance categorized vent area, flue collar area, or draft hood outlet areas.
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)] (continued)*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
SINGLE-WALL METAL CONNECTOR
SINGLE-WALL METAL CONNECTOR DIAMETER — D (inch)
TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM
8 9 10 12
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
HEIGHT
H
(feet)
LATERAL
L
(feet)
FAN NAT FAN NAT FAN NAT FAN NAT
Min Max Max Min Max Max Min Max Max Min Max Max
6 2 NA NA 247 NA NA 319 NA NA 400 NA NA 580
5 NA NA 230 NA NA 297 NA NA 375 NA NA 560
8 2 NA NA 265 NA NA 349 382 725 445 549 1021 650
5 NA NA 246 NA NA 327 NA NA 422 673 1003 638
8 NA NA 237 NA NA 317 NA NA 408 747 985 621
10 2 216 518 297 271 654 387 373 808 490 536 1142 722
5 NA NA 276 334 635 364 459 789 465 657 1121 710
10 NA NA 261 NA NA 345 547 758 441 771 1088 665
15 2 211 611 335 264 776 440 362 965 560 520 1373 840
5 261 591 312 325 755 414 444 942 531 637 1348 825
10 NA NA 294 392 722 392 531 907 504 749 1309 774
15 NA NA 278 452 692 372 606 873 481 841 1272 738
20 2 206 675 374 258 864 490 252 1079 625 508 1544 950
5 255 655 348 317 842 461 433 1055 594 623 1518 930
10 312 622 330 382 806 437 517 1016 562 733 1475 875
15 NA NA 311 442 773 414 591 979 539 823 1434 835
20 NA NA 292 NA NA 392 663 944 510 911 1394 800
30 2 200 759 420 249 982 556 340 1237 715 489 1789 1110
5 245 737 391 306 958 524 417 1210 680 600 1760 1090
10 300 703 370 370 920 496 500 1168 644 708 1713 1020
15 NA NA 349 428 884 471 572 1128 615 798 1668 975
20 NA NA 327 NA NA 445 643 1089 585 883 1624 932
30 NA NA 281 NA NA 408 NA NA 544 1055 1539 865
50 2 191 837 475 238 1103 631 323 1408 810 463 2076 1240
5 NA NA 442 293 1078 593 398 1381 770 571 2044 1220
10 NA NA 420 355 1038 562 447 1337 728 674 1994 1140
15 NA NA 395 NA NA 533 546 1294 695 761 1945 1090
20 NA NA 370 NA NA 504 616 1251 660 844 1898 1040
30 NA NA 318 NA NA 458 NA NA 610 1009 1805 970
Minimum
internal area of
chimney
(square inches)
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 areas.
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)]*
   
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
DRAFT HOOD-EQUIPPED
APPLIANCE VENT CONNECTION:
CONNECTED DIRECTLY TO PIPE OR VENT
DIAMETER — D (inch)
TO BE USED WITH CHIMNEY AREAS WITHIN THE SIZE LIMITS AT BOTTOM
3 4 5 6 7 8 10 12
HEIGHT
H
(feet)
LATERAL
L
(feet)
APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
MAXIMUM APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
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 1040
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 1190
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 1370
2 44 84 148 230 320 441 730 1140
5 NA 78 137 210 296 410 694 1080
10 NA 68 125 196 274 388 656 1050
15 NA NA 113 177 258 366 625 1000
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 1550
2 NA 95 171 260 370 492 820 1290
5 NA NA 159 234 342 474 780 1230
10 NA NA 146 221 318 456 730 1190
15 NA NA NA 200 292 407 705 1130
20 NA NA NA 185 276 384 670 1080
30 NA NA NA NA 222 330 605 1010
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
 
NUMBER OF APPLIANCES:
SINGLE
APPLIANCE TYPE:
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
H
(feet)
INTERNAL AREA OF CHIMNEY (square inches)
12 19 28 38 50 63 78 113
  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
  Local 99% winter design temperature: 27°F 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
  Local 99% winter design temperature: 17°F 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
  Local 99% winter design temperature: 5°F 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
  Local 99% winter design temperature: -10°F 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 1003
Local 99% winter design temperature: -11°F or lower
Not recommended for any vent configurations
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, °C = (°F-32)/1.8
Notes:
  1. 1 See Figure 803.1.2(6) for a map showing local 99 percent winter design temperatures in the United States.
  2. 2 NA: Not applicable.
Zero (0) lateral (L) shall apply only 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 when 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 Table 803.1.2(1) through Table 803.2(9) 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. [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 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. Where vents extend outdoors above the roof more than 5 feet (1524 mm) higher than required by Table 802.6.1, and where vents terminate in accordance with Section 802.6.1(1)(b), the outdoor portion of the vent shall be enclosed as required by this paragraph 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 R8 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 all of the following requirements are met:
  1. The vent connector is Type B double wall.
  2. The vent connector length is limited to 18 in./in. (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 not be less than 5°F (-15°C).
  6. For a space-heating appliance, the input rating is greater than 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 greater than 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 all 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 higher than shown in Table 803.1.2(1) through Table 803.2(9), 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), either 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]
Venting 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 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 when the second appliance is a fan-assisted appliance, or the NAT + NAT column when 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 when the second appliance is a fan-assisted appliance, and the FAN + NAT column shall be used when 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)]*
   
NUMBER OF APPLIANCES:
TWO OR MORE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
TYPE B DOUBLE-WALL CONNECTOR
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER — D (inch)
3 4 5 6 7
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
CONNECTOR
RISE
R
(feet)
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
6 1 22 37 26 35 66 46 46 106 72 58 164 104 77 225 142
2 23 41 31 37 75 55 48 121 86 60 183 124 79 253 168
3 24 44 35 38 81 62 49 132 96 62 199 139 82 275 189
8 1 22 40 27 35 72 48 49 114 76 64 176 109 84 243 148
2 23 44 32 36 80 57 51 128 90 66 195 129 86 269 175
3 24 47 36 37 87 64 53 139 101 67 210 145 88 290 198
10 1 22 43 28 34 78 50 49 123 78 65 189 113 89 257 154
2 23 47 33 36 86 59 51 136 93 67 206 134 91 282 182
3 24 50 37 37 92 67 52 146 104 69 220 150 94 303 205
15 1 21 50 30 33 89 53 47 142 83 64 220 120 88 298 163
2 22 53 35 35 96 63 49 153 99 66 235 142 91 320 193
3 24 55 40 36 102 71 51 163 111 68 248 160 93 339 218
20 1 21 54 31 33 99 56 46 157 87 62 246 125 86 334 171
2 22 57 37 34 105 66 48 167 104 64 259 149 89 354 202
3 23 60 42 35 110 74 50 176 116 66 271 168 91 371 228
30 1 20 62 33 31 113 59 45 181 93 60 288 134 83 391 182
2 21 64 39 33 118 70 47 190 110 62 299 158 85 408 215
3 22 66 44 34 123 79 48 198 124 64 309 178 88 423 242
50 1 19 71 36 30 133 64 43 216 101 57 349 145 78 477 197
2 21 73 43 32 137 76 45 223 119 59 358 172 81 490 234
3 22 75 48 33 141 86 46 229 134 61 366 194 83 502 263
100 1 18 82 37 28 158 66 40 262 104 53 442 150 73 611 204
2 19 83 44 30 161 79 42 267 123 55 447 178 75 619 242
3 20 84 50 31 163 89 44 272 138 57 452 200 78 627 272
  COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER — D (inch)
4 5 6 7
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
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
8 101 90 73 155 129 114 224 178 163 339 275 223
10 110 97 79 169 141 124 243 194 178 367 299 242
15 125 112 91 195 164 144 283 228 206 427 352 280
20 136 123 102 215 183 160 314 255 229 475 394 310
30 152 138 118 244 210 185 361 297 266 547 459 360
50 167 153 134 279 244 214 421 353 310 641 547 423
100 175 163 NA 311 277 NA 489 421 NA 751 658 479
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(1)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)] (continued)
 
NUMBER OF APPLIANCES:
TWO OR MORE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
TYPE B DOUBLE-WALL CONNECTOR
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER — D (inch)
8 9 10
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
CONNECTOR
RISE
R
(feet)
FAN NAT FAN NAT FAN NAT
Min Max Max Min Max Max Min Max Max
6 1 92 296 185 109 376 237 128 466 289
2 95 333 220 112 424 282 131 526 345
3 97 363 248 114 463 317 134 575 386
8 1 100 320 194 118 408 248 138 507 303
2 103 356 230 121 454 294 141 564 358
3 105 384 258 123 492 330 143 612 402
10 1 106 341 200 125 436 257 146 542 314
2 109 374 238 128 479 305 149 596 372
3 111 402 268 131 515 342 152 642 417
15 1 110 389 214 134 493 273 162 609 333
2 112 419 253 137 532 323 165 658 394
3 115 445 286 140 565 365 167 700 444
20 1 107 436 224 131 552 285 158 681 347
2 110 463 265 134 587 339 161 725 414
3 113 486 300 137 618 383 164 764 466
30 1 103 512 238 125 649 305 151 802 372
2 105 535 282 129 679 360 155 840 439
3 108 555 317 132 706 405 158 874 494
50 1 97 627 257 120 797 330 144 984 403
2 100 645 306 123 820 392 148 1014 478
3 103 661 343 126 842 441 151 1043 538
100 1 91 810 266 112 1038 341 135 1285 417
2 94 822 316 115 1054 405 139 1306 494
3 97 834 355 118 1069 455 142 1327 555
  COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER — D (inch)
8 9 10
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
FAN
+FAN
FAN
+NAT
NAT
+NAT
6 404 314 260 547 434 335 672 520 410
8 444 348 290 602 480 378 740 577 465
10 477 377 315 649 522 405 800 627 495
15 556 444 365 753 612 465 924 733 565
20 621 499 405 842 688 523 1035 826 640
30 720 585 470 979 808 605 1209 975 740
50 854 706 550 1164 977 705 1451 1188 860
100 1025 873 625 1408 1215 800 1784 1502 975
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

TABLE 803.2(1)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)] (continued)*
   
NUMBER OF APPLIANCES:
TWO OR MORE
APPLIANCE TYPE:
APPLIANCE VENT CONNECTION:
TYPE B DOUBLE-WALL CONNECTOR
VENT CONNECTOR CAPACITY
TYPE B DOUBLE-WALL VENT AND CONNECTOR DIAMETER — D (inch)
12 14 16 18
APPLIANCE INPUT RATING LIMITS IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
CONNECTOR
RISE
R
(feet)
FAN NAT FAN NAT FAN NAT FAN NAT
Min Max Max Min Max Max Min Max Max Min Max Max
6 2 174 764 496 223 1046 653 281 1371 853 346 1772 1080
4 180 897 616 230 1231 827 287 1617 1081 352 2069 1370
6 NA NA NA NA NA NA NA NA NA NA NA NA
8 2 186 822 516 238 1126 696 298 1478 910 365 1920 1150
4 192 952 644 244 1307 884 305 1719 1150 372 2211 1460
6 198 1050 772 252 1445 1072 313 1902 1390 380 2434 1770
10 2 196 870 536 249 1195 730 311 1570 955 379 2049 1205
4 201 997 664 256 1371 924 318 1804 1205 387 2332 1535
6 207 1095 792 263 1509 1118 325 1989 1455 395 2556 1865
15 2 214 967 568 272 1334 790 336 1760 1030 408 2317 1305
4 221 1085 712 279 1499 1006 344 1978 1320 416 2579 1665
6 228 1181 856 286 1632 1222 351 2157 1610 424 2796 2025
20 2 223 1051 596 291 1443 840 357 1911 1095 430 2533 1385
4 230 1162 748 298 1597 1064 365 2116 1395 438 2778 1765
6 237 1253 900 307 1726 1288 373 2287 1695 450 2984 2145
30 2 216 1217 632 286 1664 910 367 2183 1190 461 2891 1540
4 223 1316 792 294 1802 1160 376 2366 1510 474 3110 1920
6 231 1400 952 303 1920 1410 384 2524 1830 485 3299 2340
50 2 206 1479 689 273 2023 1007 350 2659 1315 435 3548 1665
4 213 1561 860 281 2139 1291 359 2814 1685 447 3730 2135
6 221 1631 1031 290 2242 1575 369 2951 2055 461 3893 2605
100 2 192 1923 712 254 2644 1050 326 3490 1370 402 4707 1740
4 200 1984 888 263 2731 1346 336 3606 1760 414 4842 2220
6 208 2035 1064 272 2811 1642 346 3714 2150 426 4968 2700
  COMMON VENT CAPACITY
TYPE B DOUBLE-WALL COMMON VENT DIAMETER — D (inch)
12 14 16 18
COMBINED APPLIANCE INPUT RATING IN THOUSANDS OF BTU PER HOUR
VENT
HEIGHT
H
(feet)
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 1284 990 815 1735 1336 1065 2253 1732 1345
8 994