GSW 5065 manual Confined Space Air Requirements for, Canadian Installations, Combined Input of

Air Requirements	b). When using a single air supply, the duct shall terminate
Important: Air for combustion and ventilation must not	within 300mm (12 in.) above and within 600mm (24 in.)
come from a corrosive atmosphere. Any failure due to cor-	horizontally of the burner level of the appliance having
rosive elements in the atmosphere is excluded from war-	the largest input. For example: GSW’s water heaters’
ranty coverage.	burners are 150mm (6 in.) from the floor, plus 300mm
Installations in or for certain places including, but not limited	(12 in.) equals 450mm (18 in.) as shown in Figure 4 (b).
to, those listed below will require outdoor air for combustion	All exterior vent openings are to be at least 300mm (12
due to chemical exposure:	in.) above the ground and clear of snow levels.

Beauty shops

Photo processing labs

(a)

Buildings with indoor pools

Water heaters installed in laundry, hobby or craft rooms

Water heaters installed near chemical storage areas

In such circumstances, outdoor combustion air may reduce,

PERMANENT

but will not eliminate the presence of corrosive chemicals in

OPENINGS

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

cals such as sulfur, fluorine and chlorine. These elements

CONFINED

UNCONFINED

are found in aerosol sprays, detergents, bleaches, cleaning

SPACE

SPACE

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

erants and many other commercial and household prod-

EQUIPMENT LOCATED IN CONFINED SPACES;

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

ALL AIR FROM INSIDE THE BUILDING.

ly corrosive acid compounds. These products should not be

stored or used near the water heater or air inlet.

(b) (12 in.)

CONFINED

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

300mm

SPACE

(MIN)

“an unconfined space” or “a confined 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

GRADE

appliances using the space. Adjacent open rooms may be

COMBINATION

included as part of the unconfined space, provided there

COMBUSTION/

are no closeable doors between these rooms. An exam-

VENTILATION

AIR DUCT

ple of this is an open basement.

600mm (24 in.)

A confined space is one smaller than described above.

450mm (18 in.)

For buildings using tight construction (newer and renovated

BASEMENT INSTALLATION, EQUIPMENT LOCATED

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

IN CONFINED SPACES; ALL AIR FROM OUTDOORS

doors, regardless of whether the space is confined or

Figure 4 Combustion Air Supply Openings And Ducts

unconfined.

(Can.)

Confined Space Air Requirements for

Combined Input of

Acceptable Round

Canadian Installations

Required

Duct Size Diameter

Refer to Figure 4 (a), or (b), and Table 1 for proper sizing

All Appliances in

Free Area

A**

B***

Confined Space*

and location of combustion air ducts and openings. CHECK

LOCAL CODES.

BTU / h

(kW / hr)

cm2

in.2

mm

in.

mm

in.

a). Two permanent openings shall be provided connecting

25,000

8

45

7

76

3

100

4

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

50,000

15

45

7

76

3

100

4

unconfined space. Each opening shall have a free area

75,000

23

70

11

100

4

125

5

of one square inch per 1,000 BTU/hour input (22

100,000

30

90

14

100

4

125

5

cm²/kW) of all appliances in the confined space. The top

125,000

37

120

18

125

5

150

6

opening shall be located as close to the ceiling as prac-

150,000

45

140

22

125

5

150

6

tical but never lower than the top of the heater. (see

Figure 4 (a)). The bottom opening shall be located nei-

* All appliances refers to, and includes, those appliances

ther more than 450mm (18 in.), nor less than 150mm (6

using the same air source (e.g. water heater, furnace,

in.), above floor level.

boiler, clothes dryer etc.).

** Maximum allowable length of ductwork listed in column

A is 6.1 equivalent metres (20 ft.).

*** Maximum allowable length of ductwork listed in column

B is 15.2 equivalent metres (50 ft.).

Table 1 Air Supply Sizing (Can.)

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