Outdoor Air Through Two Vertical Ducts
The illustrations shown in this section of the manual are a reference for the openings that provide fresh air into confined spaces only.
Do not refer to these illustrations for the purpose of vent installation. See Venting Installation on page 15 for complete venting installation instructions.
When ducts are used, they shall 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 shall be not less than 3 inches.
Air From Other Indoor Spaces
Figure 17
The confined space shall be provided with two permanent vertical ducts, one commencing within 12 inches (300 mm) of the top and one commencing within 12 inches (300 mm) of the bottom of the enclosure. The vertical ducts shall communicate directly with the outdoors. See Figure 17.
Each duct opening shall have a minimum free area of 1 square inch per 4,000 Btu/hr (550 mm2 per kW) of the aggregate input rating of all appliances installed in the enclosure.
Figure 18
The confined space shall be provided with two permanent openings, one commencing within 12 inches (300 mm) of the top and one commencing within 12 inches (300 mm) of the bottom of the enclosure. See Figure 18.
Each opening shall communicate directly with an additional room(s) of sufficient volume so that the combined volume of all spaces meets the criteria for an Unconfined Space.
Each opening shall have a minimum free area of 1 square inch per 1,000 Btu/hr (2200 mm2 per kW) of the aggregate input rating of all appliances installed in the enclosure. Each opening shall not be less than 100 square inches (645 cm2).
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