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(b) Air from Outdoors
A confined space shall be provided with two permanent
openings: one near the top, and one near the bottom of
the enclosure. These openings can be open directly to
the outdoors or by ducts to crawl spaces or attics which
are open to the outdoors.
(i) Air Supplied from Outdoors,
Table II, see Figure 2
Free
Area A
D
L
D
U
H
W
CSA B149.1
1 in
2
per 4000 BTU/Hr
6” Min., 18” Max
Note 1
3” min.
per calculation from A
U.S. ANSI Z223.1
1 in
2
per 4000 BTU/Hr
12” min.
12” min.
3” min.
per calculation from A
Table II
(ii) Air Supplied from Outdoors by Horizontal Ducts
Table III, see Figure 2
Free
Area A
D
L
D
U
H
W
CSA B149.1
1 in
2
per 2000 BTU/Hr
6” Min., 18” Max
Note 1
3” min.
per calculation from A
U.S. ANSI Z223.1
1 in
2
per 2000 BTU/Hr
12” min.
12” min.
3” min.
per calculation from A
Table III
(iii) Air Supplied from Outdoors by Vertical Ducts,
Table IV, see Figure 2
Free
Area A
D
L
D
U
H
W
CSA B149.1
1 in
2
per 4000 BTU/Hr
6” Min., 18” Max
Note 1
3” min.
per calculation from A
U.S. ANSI Z223.1
1 in
2
per 4000 BTU/Hr
12” min.
12” min.
3” min.
per calculation from A
Table IV
METHOD OF INSTALLATION
Venting Materials
Vent Pipe Material of Schedule 40 ABS, CPVC must
be used in this installation.
All materials must be of the same type for one instal-
lation and must use the appropriate solvent cement
and primer/cleaner.
Pipes and Fittings must conform to the following stan-
dards:
i) CSA standard and/or
ii) American National Standards Institute and the
American Society for Testing and Materials
(ANSI /ASTM) Standards.
VENTING CONNECTIONS
1) VENT TERMINATION
Outside Vent Terminal Location
In Canada, the vent terminal location must be in accor-
dance with the latest edition of the CSA B149.1.
Natural Gas and Propane Installation Code and Public
Utility and/or Local Codes having jurisdiction.
In the U.S., the National Fuel Gas Code, ANSI Z 223.1
(latest edition) and local codes have specific require-
ments for the location of vent terminals on vertical
walls.
The following is a condensed outline for prohibited
locations of outside vent terminals:
In Canada:
The vent shall not terminate:
– within 6’ of a mechanical air supply inlet of a build-
ing.
– above a meter regulator within 3’ horizontally of the
vertical centre line of the regulator.
– vent outlet to a maximum vertical distance of 15’.
– less than 1’ above grade level or the highest snow
accumulation level that can be expected. In areas
where high snow accumulations occur, the vent ter-
minal may have to be raised by a vertical riser.
– within 1’ of a building opening or combination air
inlet of another appliance.
– less than 7’ above a driveway or sidewalk.