b.If result is less than 50 ft3 per 1,000 Btuh, space is considered a confined space.
4.Determine building type. A building of unusually tight construction has the following characteristics:
a.Walls and ceiling exposed to outside atmosphere have a continuous water vapor retarder with a rating of 1 perm or less with openings gasketed and sealed, and
b.
c.Caulking or sealants applied in joints around window and door frames, between sole plates and floors, between
5.For boiler located in an unconfined space in a building of other than unusually tight construction, adequate combustion and ventilation air is normally provided by fresh air infiltration through cracks around windows and doors.
6.For boiler located in an unconfined space in a building of unusually tight construction or in
aconfined space, provide outdoor air through permanent opening(s) which communicate directly or by duct with the outdoors or spaces (crawl or attic) freely communicating with the outdoors. Minimum dimension of air opening(s) is 3” (7.6 cm).
a.Two permanent openings: Locate one opening within 12 inches (30.5 cm) of top of space. Locate remaining opening within 12 inches
(30.5 cm) of bottom of space. Size each opening per following:
i.Direct communication with outdoors. Minimum free area of each opening must be 1 square inch per 4,000 Btu per hour input of all equipment in space.
ii.Vertical ducts. Minimum free area of each opening must be 1 square inch per 4,000 Btu per hour input of all equipment in space. Duct
iii.Horizontal ducts. Minimum free area of each opening must be 1 square inch per 2,000 Btu per hour input of all equipment in space. Duct
b.One permanent opening shall be permitted where the boiler has clearances of at least 1” (2.5 cm) from the sides and rear and 6” (15.2 cm) from the front. Locate the opening within 12 inches (30.5 cm) of top of space. Size opening per following:
i.Minimum free area of 1 square inch per 3,000 Btu per hour input of all equipment in space.
ii.Free area shall not be less than the sum of the areas of all vent connectors in the confined space.
Alternate method for boiler located within confined space. Use indoor air if two permanent openings communicate directly with additional space(s) of sufficient volume such that combined volume of all spaces meet criteria for unconfined space. Size each opening for minimum free area of 1 square inch per 1,000 Btu per hour input of all equipment in spaces, but not less than 100 square inches.
7.Ventilation Duct Louvers and Grilles. Equip outside openings with louvers to prevent entrance of rain and snow, and screens to prevent entrance of insects and rodents. Louvers and grilles must be fixed in open position or interlocked with equipment to open automatically before burner operation. Screens must not be smaller than ¼ inch mesh.
Consider the blocking effect of louvers, grilles and screens when calculating the opening size to provide the required free area. If free area of louver or grille is not known, assume wood louvers have
8.For Specially Engineered Installations. The above requirements shall be permitted to be waived where special engineering, consistent with good engineering practice and approved by the authority having jurisdiction, provides an adequate supply of air for combustion, ventilation, and dilution of flue gases.
WARNING
Do not install boiler where gasoline or other flammable vapors or liquids, or sources of hydrocarbons (i.e. bleaches, cleaners, chemicals, sprays, paint removers, fabric softeners, etc.) are used or stored.
NOTICE