Page 571 - 2018_IRC

FUEL GAS

of all appliances in the space, but not less than 100 square Where directly communicating with the outdoors, or
2
inches (0.06 m ). One permanent opening shall where communicating with the outdoors through vertical
commence within 12 inches (305 mm) of the top and one ducts, each opening shall have a minimum free area of 1
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permanent opening shall commence within 12 inches square inch per 4,000 Btu/h (550 mm /kW) of total input
(305 mm) of the bottom of the enclosure. The minimum rating of all appliances in the enclosure [see Figures
dimension of air openings shall be not less than 3 inches G2407.6.1(1) and G2407.6.1(2)].
(76 mm).
Where communicating with the outdoors through hori-
G2407.5.3.2 (304.5.3.2) Combining spaces in differ- zontal ducts, each opening shall have a minimum free area
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ent stories. The volumes of spaces in different stories of not less than 1 square inch per 2,000 Btu/h (1100 mm /
shall be considered to be communicating spaces where kW) of total input rating of all appliances in the enclosure
such spaces are connected by one or more permanent [see Figure G2407.6.1(3)].
openings in doors or floors having a total minimum free G2407.6.2 (304.6.2) One-permanent-opening method.
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area of 2 square inches per 1,000 Btu/h (4402 mm /kW) One permanent opening, commencing within 12 inches
of total input rating of all appliances. (305 mm) of the top of the enclosure, shall be provided.
G2407.6 (304.6) Outdoor combustion air. Outdoor combus- The appliance shall have clearances of not less than 1
tion air shall be provided through opening(s) to the outdoors in inch (25 mm) from the sides and back and 6 inches (152
accordance with Section G2407.6.1 or G2407.6.2. The mini- mm) from the front of the appliance. The opening shall
mum dimension of air openings shall be not less than 3 inches directly communicate with the outdoors or through a verti-
(76 mm). cal or horizontal duct to the outdoors, or spaces that freely
G2407.6.1 (304.6.1) Two-permanent-openings method. communicate with the outdoors (see Figure G2407.6.2)
Two permanent openings, one commencing within 12 inches and shall have a minimum free area of 1 square inch per
2
(305 mm) of the top and one commencing within 12 inches 3,000 Btu/h (734 mm /kW) of the total input rating of all
(305 mm) of the bottom of the enclosure, shall be provided. appliances located in the enclosure and not less than the
The openings shall communicate directly or by ducts with sum of the areas of all vent connectors in the space.
the outdoors or spaces that freely communicate with the out-
doors.

FIGURE G2407.6.1(1) [304.6.1(1)]
ALL AIR FROM OUTDOORS—INLET AIR FROM VENTILATED CRAWL SPACE AND OUTLET AIR TO VENTILATED ATTIC
(see Section G2407.6.1)

546 2018 INTERNATIONAL RESIDENTIAL CODE ®
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