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AIR FOR COMBUSTION AND VENTILATION
DETERMINING FRESH-AIR FLOW FOR
FIREBOX 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
appliance plus any adjoining rooms with doorless
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 22 ft. (length) x 18 ft. (width)
x 8 ft. (ceiling height) = 3168 cu. ft. (volume of
space)
If additional ventilation to adjoining room is sup-
plied 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 = (Maximum
Btu/Hr the space can support)
Example: 3168 cu. ft. (volume of space) x 20 =
63,360 (maximum Btu/Hr the space can support)
3.
Add the Btu/Hr of all fuel burning appliances in
the space.
Gas water appliance*
Gas furnace
Vented gas appliance
Gas fi replace logs
Other gas appliances*
Total
* Do not include direct-vent gas appliances. Direct-
vent draws combustion air from the outdoors and
vents to the outdoors.
Example:
Gas water appliance
Gas fi rebox logs
Total
8
Continued
4.
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 support. You
must provide additional fresh air. Your options are
as follows:
A. Rework work sheet, adding the space of an
B. Vent room directly to the outdoors. See Ventila-
C. Install a lower Btu/Hr gas log appliance, if lower
If the actual Btu/Hr used is less than the maximum
Btu/Hr the space can support, the space is an un-
confi ned space. You will need no additional fresh
____________ Btu/Hr
air ventilation.
____________ Btu/Hr
____________ Btu/Hr
____________ Btu/Hr
+ ___________ Btu/Hr
= ___________ Btu/Hr
____________ Btu/Hr
30,000
+ ___________ Btu/Hr
10,000
= ___________ Btu/Hr
40,000
SuperiorFireplaces.us.com
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:
35,840 Btu/Hr (maximum the space
can support)
40,000 Btu/Hr (actual amount of Btu/
Hr used)
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, Page
9.
tion Air from Outdoors, Page 9.
Btu/Hr size makes room unconfi ned.
WARNING: If the area in which
the appliance 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.
126872-01C
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