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Fig. 7 - Air for Combustion, Ventilation, and Dilution for
Outdoors
SSpaces having at least 50 cubic feet per 1,000 Btuh may use the INDOOR COMBUSTION AIR,
STANDARD or KNOWN AIR INFILTRATION METHOD.
Outdoor Combustion Air Method
1.Provide the space with sufficient air for proper combus- tion, ventilation, and dilution of flue gases using perman- ent horizontal or vertical duct(s) or opening(s) directly communicating with the outdoors or spaces that freely communicate with the outdoors.
2.Fig. 7 illustrates how to provide TWO OUTDOOR OPENINGS, one inlet and one outlet combustion and ventilation air opening, to the outdoors.
e.One opening MUST commence within 12 in. (300 mm) of the ceiling and the second opening MUST commence within 12 in. (300 mm) of the floor.
f.Size openings and ducts per Fig. 7 and Table 2.
g.TWO HORIZONTAL DUCTS require 1 sq. in. (645 sq. mm) of free area per 2,000 Btuh (1,100 mm2/kW) of combined input for all gas appliances in the space per Fig. 7 and Table 2.
h.TWO OPENINGS OR VERTICAL DUCTS require 1
sq. in. (645 sq. mm) of free area per 4,000 Btuh (550 mm2/kW) for combined input of all gas appliances in the space per Fig. 7 and Table 2.
3.ONE OUTDOOR OPENING requires:
a.1 sq. in. (645 sq. mm) of free area per 3,000 Btuh (734 mm2/kW) for combined input of all gas appli- ances in the space per Table 2 and
b.Not less than the sum of the areas of all vent connect- ors in the space.
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*Minimum opening size is 100 sq in. (64516 sq. mm)with minimum dimensions of 3 in. (76 mm)
† Minimum of 3 in. (76 mm) when
A03175
Fig. 8 - Air for Combustion, Ventilation, and Dilution from
Indoors
The opening shall commence within 12 in. (300 mm) of the ceiling. Appliances in the space shall have clearances of at least 1 in. (25 mm) from the sides and back and 6 in. (150 mm) from the front. The opening shall directly communicate with the outdoors or shall communicate through a vertical or horizontal duct to the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.
Indoor Combustion AirE NFPA & AGA
Standard and
Indoor air is permitted for combustion, ventilation, and dilution, if the Standard or
!WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury or death.
Many homes require air to be supplied from outdoors for furnace combustion, ventilation, and dilution of flue gases.
The furnace combustion air supply must be provided in accordance with this instruction manual.
The Standard Method:
1.The space has no less volume than 50 cubic feet per 1,000 Btuh of the maximum input ratings for all gas appliances installed in the space and
2.The air infiltration rate is not known to be less than 0.40 air changes per hour (ACH).
The Known Air Infiltration Rate Method shall be used, if the infiltration rate is known to be:
1.Less than 0.40 ACH and
2.Equal to or greater than 0.10 ACH
9