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COMBUSTION AND VENTILATION AIR SUPPLY (FOR CANADA INSTALLATION)
CAUTION: All combustion air has to be drawn from the air outside the building (the mechanical equipment
room directly communicates with the outdoors).
1. Ventilation of the space occupied by the boiler shall be provided by an opening(s) for ventilation air at the highest
practical point communicating with outdoors. The total cross-sectional area of such an opening(s) shall be at
least 10% of the area required in (2) and (3), but in no case shall the cross-sectional area be less than10 square
inches (6500 square mm).
2. For boilers using a barometric damper in the vent system, and when air supply is provided by natural air flow from
the outdoors for natural draft, partial fan assisted, fan-assisted or power draft-assisted burners, there shall be a
permanent air supply opening(s) having a cross section area of not less than 1 sq. in. per 7000 BTUH
(310 sq. mm per kW) up to and including 1 million BTUH, plus 1 sq. in. per 14000 BTUH (155 sq. mm per kW) in
excess of 1 million BTUH. This opening(s) shall be either located at or ducted to a point neither more than 18
inches (450 mm) nor less than 6 inches (150 mm) above the floor level. The duct can also "Goose Neck" through
the roof. The duct is preferred straight down 18" from floor, but do not place near piping. This air supply opening
requirement shall be in addition to the air opening for ventilation air required in (1).
3. For boilers not using a barometric damper in the ventsystem, and when air supply is provided by natural air flow
from outdoors for a power burner and there is no draft regulator, draft hood or similar flue gas dilution device
installed in the same space, in addition to the opening for ventilation air required in (1), there shall be a permanent
air supply opening(s) having a total cross-sectional area of not less than 1 sq. in. for each 30,000 BTUH
(70 sq. mm per kW) of total rated input of the burner(s), and the location of the opening(s) shall not interfere with
the intended purpose of the opening(s) for ventilation air referred to (1). This opening(s) can be ducted to a point
neither more than 18 inches (450 mm) nor less than 6 inches (150 mm) above the floor level. The duct can also
"Goose Neck" through the roof. The duct is preferred to be straight down 18” from floor, but do not place near
piping.
4. Refer to the latest version of the CAN/CGA-B149.1 and .2 for additional information.
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