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Installation (Combustion Air Supply) continued-
All Air From Inside the Building: The confined space must be provided with
two permanent openings communicating directly with an additional room(s) of
sufficient volume so that the combined volume of all spaces meets the criteria
for an unconfined space. The total input of all gas utilization equipment installed
in the combined space must be considered in making this determination. Each
opening must have a minimum free area of 1 inch² (6.5 cm
(0.29 kw) per hour of the total input rating of all gas utilization equipment in the
confined space, but not less than 100 inches² (645 cm
within 12 inches (31 cm) of the top and one within 12 inches (31 cm) of the
bottom of the enclosure.
All Air From Outdoors: The confined space must be provided with two
permanent openings, one commencing within 12 inches (31 cm) of the top and
one commencing within 12 inches (31 cm) from the bottom of the enclosure.
The openings must 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 must have a
minimum free area of 1 inch² (6.5 cm
total input rating of all equipment in the enclosure.
2. When communicating with the outdoors through vertical ducts, each
opening must have a minimum free area of 1 inch² (6.5 cm
(1.2 kw) per hour of total input rating of all equipment in the enclosure.
3. When communicating with the outdoors through horizontal ducts, each
opening must have a minimum free area of 1 inch² (6.5 cm
(0.6 kw) per hour of total input rating of all equipment in the enclosure.
4. When ducts are used, they must 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 must be not less than 3 inches (7.5 cm).
Specially Engineered Installations
The requirements noted under CONFINED SPACES above must not
necessarily govern when special engineering, approved by the authority having
jurisdiction, provides an adequate supply of air for combustion, ventilation, and
dilution of flue gases.
2
2
) per 4000 BTU (1.2 kw) per hour of
22
2
) per 1000 BTU
). One opening must be
) per 4000 BTU
2
) per 2000 BTU
2
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