Each opening shall have a minimum free area of
one (1) in
2
/1,000 BTU (22.0 cm
2
/kW)
of the total
input rating of all gas appliances in the confined
space, but not less than one hundred (100) square
inches (645 cm
2
). One opening shall commence within
six (6) inches (15.2 cm) of the top and one within six (6)
inches (15.2 cm) of the bottom of the enclosure.
2) All Air From Outdoors:
The confined space shall be provided with two
permanent openings, one commencing within six (6)
inches (15.2 cm) of the top and one commencing
within six (6) inches (15.2 cm) from the bottom of the
enclosure. The openings shall communicate directly
or by ducts, with the outdoors or spaces (crawl or
attic) that freely communicate with the outdoors.
A) When communicating directly with the outdoors,
each opening shall have a minimum free area of
one (1) in
2
/4,000 BTU (5.5 cm
2
/kW)
of the total input
rating of all gas appliances in the enclosure (see
Figure 5).
B) When communicating with the outdoors through
vertical ducts, each opening shall have a minimum
free area of
one (1) in
2
/4,000 BTU (5.5 cm
2
/kW)
of
the total input rating of all gas appliances in the
enclosure (see Figure 6).
C) When communicating with the outdoors through
horizontal ducts, each opening shall have a minimum
free area of
one (1) in
2
/2,000 BTU (11.0 cm
2
/kW)
of
the total input rating of all gas appliances in the
enclosure (see Figure 7).
When ducts are used, they shall be of the same
cross-sectional area as the free area of the openings
to which they connect. The minimum short side
dimension of rectangular air ducts shall not be less
than three (3) inches (7.62 cm).
Louvers and Grilles
In calculating free area for ventilation and combustion
air supply openings, consideration must be given to
the blocking effect of louvers, grilles, or screens pro-
tecting the openings. Screens must not be smaller
5
INSTALLATION INSTRUCTIONS
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 7
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 6
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 5
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 4
