Air Requirements, Canadian Installations

Air Requirements

Note: The top opening shall not be lower than the top of the

Important: Air for combustion and ventilation must not

heater. The location of the bottom opening shall be 150-

come from a corrosive atmosphere. Any failure due to cor-

450mm (6-18 in.) above floor level.

rosive elements in the atmosphere is excluded from war-

Note: Ensure sufficient ventilation air to prevent elevat-

ranty coverage.

Installations in or for certain places including, but not limited

ed temperatures in closets and ventilated spaces.

to, those listed below may require outdoor air for combus-

When an exhaust fan is installed in the same room as the

tion to reduce the risk of chemical exposure:

water heater, the supply air openings must be of sufficient

• Beauty shops, Photo processing labs

capacity to prevent a backflow of air through the water

• Buildings with indoor pools

heater exhaust venting.

• Water heaters installed in laundry, hobby or craft rooms

b). When using a single air supply, the duct shall terminate

• Water heaters installed near chemical storage areas

In such circumstances, outdoor combustion air may reduce,

within 300mm (12 in.) above and within 600mm (24 in.)

but will not eliminate the presence of corrosive chemicals in

horizontally of the burner level of the appliance having

the air. Combustion air must be free of acid-forming chemi-

the largest input.

cals such as sulfur, fluorine and chlorine. These elements

Refer to latest edition of the "Natural Gas and Propane

are found in aerosol sprays, detergents, bleaches, cleaning

solvents, air fresheners, paint and varnish removers, refrig-

Installation Codes" CAN/CSA-B149-1 for air supply duct

erants and many other commercial and household prod-

sizes.

ucts. When burned, vapours from these products form high-

ly corrosive acid compounds. These products should not be

stored or used near the water heater or air inlet.

The area in which the heater is located is classified as either

"an unconfined space" or "a ventilated space."

An unconfined space is defined as a space having a vol-

ume not less than 50 cubic feet per 1000 BTU/hour (4.8

cubic metres per kilowatt) of combined input rating of all

appliances using the space. Adjacent open rooms may be

included as part of the unconfined space, provided there

are no closeable doors between these rooms. An exam-

ple of this is an open basement.

(a)

A ventilated space is one smaller than described above.

For buildings using tight construction (newer and renovated

structures), the air supply shall be introduced from the out-

doors, regardless of whether the space is confined or

unconfined. CHECK LOCAL CODES.

PERMANENT

Ventilated Space Air Requirements for

OPENINGS

SPACE

UNCONFINED

Canadian Installations

VENTILATED

Refer to Figure 4 (a), or (b), for proper sizing and location of

SPACE

combustion air ducts and openings. CHECK LOCAL

CODES.

EQUIPMENT LOCATED IN VENTILATED

a). Two permanent openings shall be provided connecting

SPACES; ALL AIR FROM INSIDE THE BUILDING.

to ventilated space (e.g. closet, small room) with the

unconfined space. Each opening shall be equal or

(b)

300mm

VENTILATED

(12 in.)

SPACE

greater than 645cm2 (100 in2.) with a width to height

(MIN)

ratio of 2:1. The top opening shall be located close to

the ceiling.

GRADE

COMBINATION

COMBUSTION/

VENTILATION

AIR DUCT

600mm (24 in.)

300mm (12 in.)

BASEMENT INSTALLATION, EQUIPMENT LOCATED

IN VENTILATED SPACES; ALL AIR FROM OUTDOORS

Figure 4a Air Opening Locations

Figure 4 Combustion Air Supply Openings And Ducts

(Can.)

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