28040-3-0511
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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 heater, 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 (Figure 6)
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 6). You can also remove door into adjoining room
(see option 3, Figure 6). 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 6
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 (Figure 7)
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 heater 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 7
pROVISIONS FOR ADEqUATE COMBUSTION & VENTILATION AIR (continued)
A1
A2
B1
B2
A1 x B1 = C1
A2 x B2 = C2
C1 + C2 = Sq. In. Required
Example:
For a 30,000 BTU Heater, 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 8
