7
(b)
All Air from Outdoors:
The confined space shall be
provided with two permanent openings, one commenc-
ing 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 com-
municate 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. (See Fig-
ure 2)
Figure 2
Equipment Located in Confined Spaces;
All Air from OutdoorsInlet Air from
Ventilated Crawl Space and Outlet Air to
Ventilated Attic. See 5.3.3-b
2. When communicating with the outdoors through
vertical ducts, 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 enclo-
sure. (See Figure 3.)
Figure 3
Equipment Located in Confined Spaces;
All Air from Outdoors Through Ventilated
Attic. See 5.3.3-b.
3. When communicating with the outdoors through
horizontal ducts, each opening shall have a mini-
mum free area of 1 square inch per 2,000 BTU per
hour of total input rating of all equipment in the
enclosure. (See Figure 4)
*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 one square
inch per 4,000 BTU per hour of the total input rating of all appliances in the enclosure.
Figure 4
Equipment Located in Confined Spaces;
All Air from Outdoors. See 5.3.3-b.
4. When ducts are used, they shall be of the same
cross-sectional area as the free area of the open-
ings to which they connect. The minimum dimen-
sion of rectangular air ducts shall not be less than 3
inches.
