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Equipment Located in Confined Spaces: All Air from
Outdoors—Inlet Air from Ventilated Crawl Space and
Outlet Air to Ventilated Attic. See 5.3.3-b.
NOTE: The inlet and outlet air openings must each have a free
area of not less than 1 sq. in. (6.5 cm
input rating of all equipment in the enclosure.
G
H
A. Chimney or gas vent
B. Ventilation louvers
(each end of attic)
C. Outlet air
D. Inlet air
2. When communicating with the outdoors through vertical
ducts, each opening shall have a minimum free area of
1 sq. in. (6.5 cm
2
) per 4,000 Btu/h of total input rating of
all equipment in the enclosure.
Equipment Located in Confined Spaces: All Air from
Outdoors Through Ventilated Attic. See 5.3.3-b.
NOTE: The inlet and outlet air openings must each have a free
area of not less than 1 sq. in. (6.5 cm
input rating of all equipment in the enclosure.
A
F
A. Chimney or gas vent
B. Ventilation louvers
(each end of attic)
C. Outlet air
3. When communicating with the outdoors through
horizontal ducts, each opening shall have a minimum free
area of 1 sq. in. (6.5 cm
rating of all equipment in the enclosure.
10
2
) per 4,000 Btu of the total
A
B
C
F
D
E
E. Ventilation louvers for
unheated crawl space
F. Water heater
G. Furnace
H. Alternate air inlet
2
) per 4,000 Btu of the total
B
C
E
D
D. Inlet air duct (ends 12"
[30.5 cm] above floor)
E. Water heater
F. Furnace
2
) per 2,000 Btu/h of total input
Equipment Located in Confined Spaces: All Air from
Outdoors. See 5.3.3-b.
NOTES:
The air duct openings must each have a free area of not less
2
than 1 sq. in. (6.5 cm
) per 2,000 Btu of the total input rating
of all equipment in the enclosure.
If the appliance room is located against an outside wall and
the air openings communicate directly with the outdoors,
each opening shall have a free area of not less than 1 sq. in.
2
(6.5 cm
) per 4,000 Btu/h of the total input rating of all
appliances in the enclosure.
A
E
A. Chimney or gas vent
B. Outlet air duct
C. Inlet air duct
4. When ducts are used, they shall be of the same cross-
sectional area as the free area of the openings to which
they connect. The minimum dimension of rectangular air
ducts shall not be less than 3" (7.6 cm).
Equipment Located in Confined Spaces: All Air from
Outdoors—Single Air Opening. See 5.3.3-b.
NOTE: The single opening must each have a free area of not less
than 1 sq. in. (6.5 cm
2
) per 3,000 Btu of the total input rating of all
equipment in the enclosure, but not less than the sum of the
areas of all vent connectors in the confined space.
A
E
A. Chimney or gas vent
B. Opening
C. Alternate opening location
5. When directly communicating with the outdoors, the
single opening shall have a minimum free area of 1 sq. in.
2
(6.5 cm
) per 3,000 Btu/h of total input rating of all
equipment in the enclosure.
B
D
C
D. Water heater
E. Furnace
B
D
C
D. Water heater
E. Furnace
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