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AIR FOR COMBUSTION
AND VENTILATION
Continued
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free heater
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas appliances* + _______ Btu/Hr
Total
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater
Vent-free heater
Total
4. Compare the maximum Btu/Hr the space can
support with the actual amount of Btu/Hr used.
__________ Btu/Hr (maximum the space
can support)
__________ Btu/Hr (actual amount of
Btu/Hr used)
57,600 Btu/Hr (maximum the
Example:
space can support)
73,000 Btu/Hr (actual amount
of Btu/Hr used)
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 Ven-
tilation 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 maxi-
mum Btu/Hr the space can support, the space is
an unconfined space. You will need no additional
fresh air ventilation.
110112-01C
_______ Btu/Hr
_______ Btu/Hr
_______ Btu/Hr
_______ Btu/Hr
_______ Btu/Hr
= _______ Btu/Hr
40,000
_______ Btu/Hr
33,000
+ _______ Btu/Hr
73,000
= _______ Btu/Hr
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WARNING: If the area in
which the heater may be oper-
ated is smaller than that defined
as an unconfined space or if the
building is of unusually tight
construction, provide adequate
combustion and ventilation air
by one of the methods described
in the National Fuel Gas Code,
ANSI Z223.1/NFPA 54 Section 5.3
or applicable local codes.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining un-
confined space. When ventilating to an adjoining
unconfined space, you must provide two perma-
nent 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 3). You
can also remove door into adjoining room (see
option 3, Figure 3). Follow the National Fuel Gas
Code, ANSI Z223.1/NFPA 54, Section 5.3, Air for
Combustion and Ventilation for required size of
ventilation grills or ducts.
Ventilation
Grills
Into Adjoining
Or
Room,
Remove
Option 1
Door into
Adjoining
Room,
Option
3
12"
Figure 3 - Ventilation Air from Inside
Building
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 within 12"
of the floor. Connect these items directly to the
outdoors or spaces open to the outdoors. These
spaces include attics and crawl spaces. Follow the
National Fuel Gas Code, ANSI Z223.1/NFPA 54,
Section 5.3, Air for Combustion and Ventilation for
required size of ventilation grills or ducts.
12"
Ventilation Grills
Into Adjoining Room,
Option 2
7
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