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8
DETERMINING FRESH-AIR FLOW
FOR FIREPLACE LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a
confined or unconfined space.
Space: Includes the room in which you will install
fireplace plus any adjoining rooms with doorless pas-
sageways 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 16 ft. (length) x 14 ft.
(width) x 8 ft. (ceiling height) = 1792 cu. ft. (vol-
ume 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 = (Maxi-
mum Btu/Hr the space can support)
Example:
1792 cu. ft. (volume of space) x 20 =
35,840 (maximum Btu/Hr the space can support)
3. Add the Btu/Hr of all fuel burning appliances in
the space.
Vent-free fireplace _________ 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. Di-
rect-vent draws combustion air from the outdoors
and vents to the outdoors.
Example:
Gas water heater _________ Btu/Hr
Vent-free fireplace + _________ Btu/Hr
Total = _________ Btu/Hr
4. Compare the maximum Btu/Hr the space can sup-
port 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)
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 unconfined
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
.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining uncon-
fined space. When ventilating to an adjoining un-
confined space, you must provide two permanent
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 4, page 9). You can also
remove door into adjoining room (see option 3, Fig-
ure 4, page 9). Follow the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, Section 5.3, Air for Com-
bustion and Ventilation for required size of ventila-
tion 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.
AIR FOR COMBUSTION
AND VENTILATION
Continued
30,000
10,000
40,000