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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
2
considered in making this determination. Each opening must have a minimum free area of 1 in.
/1000 BTU
2
(2.54cm
/0.29kW) per hour of the total input rating of all gas utilization equipment in the confined space, but not less than
2
100 square inches (254cm
). One opening must be within 12 inches (30.5 cm) of the top and one within 12 inches (30.5
cm) of the bottom of the enclosure.
UNCONFINED SPACES
In unconfined spaces in buildings, infiltration may be adequate to provide air for combustion, ventilation and dilution of flue
gases. However, in buildings of tight construction (for example, weather stripping, heavily insulated, caulked, vapor barrier,
etc.), additional air may need to be provided using the methods described above under CONFINED SPACES: All Air From
Outdoors or SPECIALLY ENGINEERED INSTALLATIONS.
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.
14
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