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111604-01E
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Example:
Gas water heater
_____________ Btu/Hr
Vent-free fireplace
_____________ Btu/Hr
Total
_____________ Btu/Hr
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)
Example:
51,200 Btu/Hr (maximum the space
can support)
73,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the 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 ad-
ditional fresh air. Your options are as follows:
A. Rework worksheet, adding the space of an adjoin-
ing room. If the extra space provides an uncon-
fined 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 Ventila-
tion 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 un-
confined space. You will need no additional fresh
air ventilation.
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
.
40,000
33,000
73,000
AIR FOR COMBUSTION
AND VENTILATION
Continued
Figure 4 - Ventilation Air from Outdoors
Figure 3 - Ventilation Air from Inside
Building
Outlet
Air
Ventilated
Attic
Outlet
Air
Inlet
Air
Inlet Air
Ventilated
Crawl Space
To
Crawl
Space
To Attic
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
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 Air From Outdoors
Provide extra fresh air by using ventilation grills
or ducts. You must provide two permanent open-
ings: 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.
IMPORTANT:
Do not provide openings for inlet
or outlet air into attic if attic has a thermostat-con-
trolled power vent. Heated air entering the attic
will activate the power vent.
