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PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR (continued)
The space in the above example is a confined space because
the actual BTU/Hr used is more than the maximum BTU/HR the
space can support. You must provide additional fresh air. Your
options are as follows:
A. Rework worksheet, adding the space of an adjoining room. If
the extra space provides an unconfined space, remove door
to adjoining room or add ventilation grills between rooms.
See
Ventilation Air From Inside Building.
B. Vent room directly to the outdoors. See
Ventilation Air
From Outdoors.
C. Install a lower BTU/Hr fireplace, if lower BTU/Hr size makes
room unconfined.
If the actual BTU/Hr used is less than the maximum BTU/Hr the
space can support, the space is an unconfined space. You will
need no additional fresh air ventilation.
WARNING
You must provide additional ventilation air in a confined space.
Ventilation Air
Ventilation Air From Inside Building
This fresh air would come from an adjoining unconfined space.
When ventilating to an adjoining unconfined space, you must
provide two permanent openings: one within 12" of the ceiling
and one within 12" of the floor on the wall connecting the two
spaces
(see options 1 and 2, Figure 32
). You can also remove
door into adjoining room
(see option 3, Figure 32).
Each
ventilation grill or opening shall have a minimum free area of one
square inch per 1,000 BTUH of the total input rating of the gas
equipment in the confined space.
Figure 4
WARNING
Rework worksheet, adding the space of the adjoining
unconfined space. The combined spaces must have enough
fresh air to supply all appliances in both spaces.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or ducts. You
must provide two permanent openings: one within 12" of the
ceiling and one with 12" of the floor. Connect these items
directly to the outdoors or spaces open to the outdoors. These
spaces include attics and crawl spaces. In most cases for direct
communication with the outdoors or direct communication
through a vertical duct a free area opening of one square inch per
4,000 BTU/Hr of fireplace input rating for each grill. If a horizontal
duct is used, a grill free area or duct opening shall have a free
area opening of one square inch per 2,000 BTU/Hr for each grill.
Follow the
National Fuel Code ANSI Z223.1/NFPA54, Air for
Combustion and Ventilation
for required size of ventilation grills
or ducts.
IMPORTANT:
Do not provide openings for inlet or outlet air into
attic if attic has a thermostat-controlled power vent. Heated air
entering the attic will activate the power vent.
Figure 5
A1
A2
B1
B2
A1 x B1 = C1
A2 x B2 = C2
C1 + C2 = Sq. In. Required
Example:
For a 30,000 BTU Fireplace, 1 sq in per 1,000 BTU
equals 30 sq. in. of opening.
(A1) 5in
2
x (B1) 3in
2
= (C1) 15in
2
(A2) 5in
2
x (B2) 3in
2
= (C2) 15in
2
(C1) 15in
2
+ (C2) 15in
2
= 30in
2
Figure 6