7
2.0
Combustion Air Venting
2.4
Methods of Accessing Combustion
Air Into A Space - Category IV
2.4.1 Indoor Combustion Air
The methods listed in this section for
accessing Indoor Combustion Air
assume that the infiltration rate is ade-
quate and not less than .40 ACH. For
infiltration rates less than .40 ACH, ref-
erence the NFPA 54 National Fuel Gas
Code for additional guidance.
Opening Size and Location
Openings used to connect indoor spaces shall
be sized and located in accordance with the
following, see Fig. 1:
- Combining spaces on the same story.
Each opening shall have a minimum
free area of 1 sq. in./1000 Btu/hr of the
total input rating of all gas utilization
equipment in the space, but not less than
100 sq. inches. One opening shall com-
mence within 12 inches of the top, and
one opening shall commence within 12
inches of the bottom of the enclosure.
The minimum dimension of air open-
ings shall be not less than 3 inches.
- Combining spaces in different stories.
The volumes of spaces in different sto-
ries shall be considered as communicat-
ing spaces where such spaces are con-
nected by one or more openings in
doors or floors having a total minimum
free area of 2 sq. in./1000 Btu/hr of
total input rating of all gas utilization
equipment.
2.4.2 Outdoor Combustion Air
Isolating the combustion appliance room
from the rest of the building and bring-
ing in uncontaminated outside air for
combustion and ventilation is always
preferred.
Opening Size and Location
The minimum dimension of air openings shall
be not less than 3 inches
Openings used to supply combustion and ven-
tilation air shall be sized and located in accor-
dance with the following:
2.4.2.1 One Permanent Opening Method
One permanent opening, commencing within 12
in. of the top of the enclosure, shall be provided
as shown in Fig 2 on page 8. The equipment
shall have clearances of at least 1 inch from the
sides and 6 in. from the front of the appliance.
The opening shall directly communicate with the
outdoors or shall communicate through a vertical
or horizontal duct to the outdoors or spaces that
freely communicate with the outdoors and shall
have a minimum free area of the following:
- 1sq. in./3000 Btu/hr of the total input
rating of all equipment located in the
enclosures, and
- Not less than the sum of the areas of all
vent connectors in the space.
NOTICE
BEST PRACTICE
All Combustion Air from Adjacent
Indoor Spaces Through Indoor
Combustion Openings
Fig. 1:
