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Air Requirements for Canadian
Installations
Canadian Codes allow for the use of a single air supply source.
Canadian customers and authorities having jurisdiction may use
the sizing listed in Table 1. Check Local Codes.
When using a single air supply, the duct shall terminate within 1
foot (30 cm) above and within 2 feet (60 cm) horizontally from
the burner level of the appliance having the largest input as shown
in Figure 3 (b), (c) and (d).
An opening shall be located neither more than 18 inches (450
mm), nor less than 6 inches (150 mm), above floor level. See
Figure 3 (b), (c) and (d).
Two permanent openings shall be provided connecting the
confined space (e.g., closet/small room) with the unconfined
space. Each opening shall have a free area of one square inch per
1,000 BTU/hour input (5.5 cm²/kW) of all appliances in the
confined space. The top opening shall commence within 12" (30
cm) of the top of space and the bottom opening shall commence
within 12" (30 cm) of the bottom of the enclosure. See Figure 3
(a).
All exterior vent openings are to be clear of snow levels.
Table 1
Acceptable Round
Duct Size Diameter
Combined Input of All
Appliances in Confined
Space*
Required
Free Area
A
1
B
2
BTU/hr (KW/hr) In.
2
cm
2
In. mm In. mm
25,000 (8) 7(45) 3(75) 4(100)
50,000 (15) 7(45) 3(75) 4(100)
75,000 (23) 11 (70) 4(100) 5(125)
100,000 (30) 14(90) 4(100) 5(125)
125,000 (37) 18(120) 5(125) 6(150)
150,000 (45) 22(140) 5(125) 6(150)
1 Maximum length of ducts in column A is 20 equivalent feet (6.1
meters)
2 Maximum length of ducts in column B is 50 equivalent feet (15.2
meters)
* All appliances refers to and includes those appliances using the
same air source. e.g. Water heater, furnace, boiler, clothe dryer, etc.