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113195-01A
7
Confined and Unconfined Space
The National Fuel Gas Code ANSI Z223.1/NFPA
54
defines a confined space as a space whose vol-
ume is less than 50 cubic feet per 1,000 Btu per
hour (4.8 m
3
per kw) of the aggregate input rating
of all appliances installed in that space and an un-
confined space as a space whose volume is not less
than 50 cubic feet per 1,000 Btu per hour (4.8 m
3
per kw) of the aggregate input rating of all appli-
ances installed in that space. Rooms communicat-
ing directly with the space in which the appliances
are installed*, through openings not furnished with
doors, are considered a part of the unconfined space.
* Adjoining rooms are communicating only if there
are doorless passageways or ventilation grills be-
tween them.
DETERMINING FRESH-AIR FLOW
FOR HEATER 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 22 ft. (length) x 18 ft.
(width) x 8 ft. (ceiling height) = 3168 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:
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.
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
AIR FOR COMBUSTION
AND VENTILATION
Continued
* 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
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:
63,360 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 maxi-
mum Btu/Hr the space can support. You must pro-
vide additional 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,
page 8
.
B. Vent room directly to the outdoors. See
Ventila-
tion Air From Outdoors,
page 8
.
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 uncon-
fined space. You will need no additional fresh air ven-
tilation.
WARNING: If the area in
which the fireplace may be op-
erated is smaller than that de-
fined as an unconfined space or
if the building is of unusually
tight construction, provide ad-
equate combustion and ventila-
tion air by one of the methods
described in the
National Fuel
Gas Code, ANSI Z223.1/NFPA
54 Section 5.3
or applicable lo-
cal codes
.
40,000
33,000
73,000
