3 Appliances Located in Unconfined Spaces:
For installations in unconfined spaces with other
than unusually tight construction, the supply of air
for combustion and ventilation can usually be
considered adequate.
4. Unusually Tight Construction:
For equipment located in buildings of unusually tight
construction as defined on the previous page,
provide air for combustion and ventilation using the
methods described in 5a or 5b below.
5. Appliances Located in Confined Spaces:
a. All air from inside the building: Provide two
permanent openings communicating directly with
an additional room or rooms of sufficient volume
so that the combined volume of all spaces meets
the criteria for an unconfined space. Use the total
input of all gas utilization equipment installed in
the combined space in making this
determination.
Size each opening with a minimum free area of
one square inch per 1000 Btu/hr. of the total
rating of all gas utilization equipment in the
confined space, but not less than I00 square
inches. Begin with one opening 12 inches from
the top, and begin the other opening within 12
inches of the bottom of the enclosure. See Figure
1. Provide air openings with minimum
dimensions not less than three (3) inches.
b. All air from outside the building. Connect the
confined space with the outdoors in accordance
with methods i) or ii) below. Provide air openings
with minimum dimensions not less than three (3)
inches. Where ducts are used, make certain that
they are the same cross-sectional area as the free
area of the openings to which they connect.
Provide two permanent openings, one
commencing within 12 inches of the top and
one commencing within 12 inches of the
bottom of the enclosure. Connect the
openings directly or by duets, with the
outdoors or spaces (crawl or attic) that freely
communicate with the outdoors.
Where directly communicating with the
outdoors (see Figure 2) or where
communicating to the outdoors through
vertical ducts (see Figure 3), size each
opening with a minimum free area of one (I)
square inch per 4000 Btu/hr. of total rating of
all equipment in the enclosure.
i ?
I
12" max
TWO AIR OPENINGS:
Minimum
Free Area Each -
1 in2per 1000 Btuh
at Least 100 in2
BUILDING
Must communicatefreely
withoutdoors
Must not beunder
negativepressure
12" max
Figure 1: Air Openings - All Air from Indoors
TWO AIR OPENINGS:
Minimum
Free Area Each -
1 in_per 4000 Btuh
Figure 2: Air Openings - All Air Directly from
Outdoors
Figure 3: Air Openings - All Air from Outdoors
through Vertical Ducts
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