FIGURE 6
FIGURE 7
PAGE 6
and shall have the same cross-sectional area of the openings to which they are connected.
4. When air for combustion and ventilation is from inside buildings, the confined space shall
be provided with two permanent openings, one starting 12 inches from the top and one 12
inches from the bottom of the enclosed space. Each opening shall have a minimum free area
of 1 square inch per one thousand (1000) BTU per hour of the total input rating of all appliances
in the enclosed space, but must not be less than one hundred (100) square inches. These
openings must freely communicate directly with other spaces of sufficient volume so that the
combined volume of all spaces meets the criteria for an unconfined space. See figure 6 below.
5. When the boiler is installed in a confined space and all air is provided from the outdoors
the confined space shall be provided with one or two permanent openings according to
methods A or B below. When ducts are used, they shall be of the same cross sectional area
as the free area of the area of the openings to which they connect. The minimum dimension
of rectangular air ducts shall be not less than 3 x 3 inches or 9 square inches.
A. When installing two openings, one must commence within 12 inches from the top and
the other within 12 inches from the bottom of the enclosure. The openings shall communicate
directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely communicate with
the outdoors. One of the following methods must be used to provide adequate air for
ventilation and combustion.
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 figure 7 above.
2. When communicating with the outdoors by means of vertical ducts, each
opening shall have a minimum free area 1 square inch per 4,000 BTU per hour of total input
rating of all appliances in the enclosed space. See figure 8 on page 7.
3. If horizontal ducts are used, each opening and duct shall have a minimum free
area 1 square inch per 2,000 BTU per hour of total input rating of all appliances in the enclosed
space. See figure 9 below.
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