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AIR FOR COMBUSTION AND VENTILATION
Use this work sheet to determine if you have
a confi ned or unconfi ned space.
Space: Includes the room in which you will install
fi replace plus any adjoining rooms with door-
less passageways or ventilation grills between
the rooms.
1. Determine the volume of the space (length
x width x height).
Length x Width x Height =__________cu. ft.
(volume of space)
Example: Space size 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2,560 cu. ft.
(volume of space)
If additional ventilation to adjoining room
is supplied with grills or openings, add the
volume of these rooms to the total volume
of the space.
2. Multiply the space volume by 20 to determine
the maximum Btu/Hr the space can support.
________ (volume of space) x 20 = (Maxi-
mum Btu/Hr the space can support)
Example: 2,560 cu. ft. (volume of space) x
f i r e - p a r t s . c o m
20 = 51,200 (maximum Btu/Hr the space can
support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free fi replace
Gas water heater*
Gas furnace
Vented gas heater
Gas fi replace 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 _____________ Btu/Hr
Vent-free fi replace + ___________ Btu/Hr
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)
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 confi ned 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:
900781-00_NC
Continued
_________ Btu/Hr
_________ Btu/Hr
_________ Btu/Hr
_________ Btu/Hr
_________ Btu/Hr
= ________ Btu/Hr
40,000
39,000
79,000
= ____________ Btu/Hr
SuperiorFireplaces.US.com
A. Rework worksheet, adding the space of an
adjoining room. If the extra space provides an
unconfi ned 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 Page 10.
C. Install a lower Btu/Hr fi replace, if lower Btu/
Hr size makes room unconfi ned.
If the actual Btu/Hr used is less than the maxi-
mum Btu/Hr the space can support, the space is
an unconfi ned space. You will need no additional
fresh air ventilation.
WARNING: If the area in which
the heater may be operated does not
meet the required volume for indoor
combustion air, combustion and
ventilation air shall be provided by
one of the methods described in the
National Fuel Gas Code, ANSI Z223.1/
NFPA 54, the International Fuel Gas
Code, or applicable local codes.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining
unconfi ned space. When ventilating to an
adjoining unconfi ned space, you must provide
two permanent openings: one within 12" of the
ceiling and one within 12" of the fl oor on the
wall connecting the two spaces (see options
1 and 2, Figure 4). You can also remove door
into adjoining room (see option 3, Figure 4).
Follow the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, Air for Combustion and
Ventilation for required size of ventilation
grills or ducts.
Ventilation
Ventilation Grills
Grills
Into Adjoining Room,
Into Adjoining
Or
Room,
Remove
Option 1
Door into
Adjoining
Room,
Option
3
12"
Figure 4 - Ventilation Air from Inside
Building
12"
Option 2
9
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