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110112-01C
7
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free heater _______
Btu/Hr
Gas water heater* _______
Btu/Hr
Gas furnace _______
Btu/Hr
Vented gas heater _______
Btu/Hr
Gas fireplace logs _______
Btu/Hr
Other gas appliances* + _______
Btu/Hr
Total = _______
Btu/Hr
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater _______
Btu/Hr
Vent-free heater + _______
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: 57,600 Btu/Hr (maximum the
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 V
en-
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.
AIR FOR COMBUSTION
AND VENTILATION
Continued
40,000
33,000
73,000
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.
Figure 3 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option
2
Ve
ntilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
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.