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AIR FOR COMBUSTION AND VENTILATION
standard method defi nes a confi ned space as
a space whose volume is less than 50 cubic
feet per 1,000 Btu/hr (4.8 m
gregate input rating of all appliances installed
in that space and an unconfi ned space as
a space whose volume is not less than 50
cubic feet per 1,000 Btu/hr (4.8 m
the aggregate input rating of all appliances
installed in that space. Rooms communicating
directly with the space in which the appliances
are installed*, through openings not furnished
with doors, are considered a part of the un-
confi ned space.
Where the air infi ltration rate of a structure is
known, the Known Air Infi ltration Rate Method
may be used. Follow The National Fuel Gas
Code, ANSI Z223.1/NFPA 54 to use this
method to determine if the space is confi ned
or unconfi ned.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Determining if You Have a Confi ned or
Unconfi ned Space Using the Standard
Method
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) = 2560 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: 2560 cu. ft. (volume of space) x 20
= 51,200 (maximum Btu/Hr the space can
support)
3. Add the Btu/Hr of all fuel-burning appliances
in the space.
126818-01C
Continued
per kw) of the ag-
3
3
per kw) of
4. Compare the maximum Btu/Hr the space
The space in the above example is a confi ned
space because the actual Btu/Hr used is more
than the maximum Btu/Hr the space can sup-
port. You must provide additional fresh air. Your
options are as follows:
A. Rework worksheet, adding the space of an
B. Vent room directly to the outdoors. See
C. Install a lower Btu/Hr heater, if lower Btu/Hr
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.
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.
SuperiorFireplaces.US.com
Vent-free fi replace
__________ Btu/Hr
Gas water heater*
__________ Btu/Hr
Gas furnace
__________ Btu/Hr
Vented gas heater
__________ Btu/Hr
Gas fi replace 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 fi replace
+ _________ Btu/Hr
Total
= _________ Btu/Hr
can support with the actual amount of Btu/
Hr used.
______Btu/Hr (maximum the space can
support)
______Btu/Hr (actual amount used)
Example: 51,200 Btu/Hr (maximum the
space can support)
73,000 Btu/Hr (actual amount of
Btu/Hr used)
adjoining room. If the extra space provides
an unconfi ned space, remove door to adjoin-
ing room or add ventilation grills between
rooms. See Ventilation Air From Inside
Building, Page 8.
Ventilation Air From Outdoors, Page 8.
size makes room unconfi ned.
WARNING: If the area in which
40,000
33,000
73,000
7
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