installed in the combined space shall be considered in making
this determination. Each opening shall have a minimum free
area of 1 square inch per 1,000 BTU per hour of the total input
rating of all gas utilization equipment in the confined space, but
not less than 100 square inches. One opening shall be within 12
inches of the top and one within 12 inches of the bottom of the
enclosure (Figure 1 ).
Chimney or Gas Vent
NOTE: Each opening must have
a free area of not less than one
square inch per 1000 BTU of
the total input rating of all equip-
ment in the enclosure, but not
less than 100 square inches.
Opening
Water
Heater
Furnace
Opening
Figure 1
Equipment Located in Confined Spaces; All
Air from Inside Building. See 5.3.3-a
.
(b) All Air from Outdoors: The confined space shall be provided
with two permanent openings, one commencing within 12
inches of the top and one commencing within 12 inches of the
bottom of the enclosure. The openings shall communicate
directly, or by ducts, with the outdoors or spaces (crawl or attic)
that freely communicate with the outdoors.
1. When directly communicating with the outdoors, each
opening shall have a minimum free area of 1 square inch per
4,000 BTU per hour of total input rating of all equipment in
the enclosure (Figure 2).
Chimney or Gas Vent
Ventilation louvers
(each end of attic)
NOTE: The inlet and outlet air
openings must each have a free
area of not less than one square
inch per 4000 BTU of the
total input rating of all equipment
in the enclosure.
Outlet Air
Water
Heater
Furnace
Inlet Air
Alternate
air inlet
Ventilation louvers for
unheated crawl space
Figure 2
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