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114668-01F
7
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54
defines a confined space as a space
whose volume is less than 50 cubic feet per
1,000 Btu/hr (4.8 m
3
per kw) of the aggregate
input rating of all appliances installed in that
space and an unconfined space as a space
whose volume is not less than 50 cubic feet
per 1,000 Btu/hr (4.8 m
3
per kw) of the ag
-
gregate 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
-
confined space.
* 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 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 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 sup-
port.
________ (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.
AIR FOR COMbUSTION AND VENTILATION
Continued
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 appl __________ 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 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:
51,200 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 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
adjoining room. If the extra space provides
an unconfined space, remove door to adjoin
-
ing room or add ventilation grills between
rooms. See
Ventilation Air From Inside
Building
, page 8
.
B. Vent room directly to the outdoors. See
Ventilation 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 maxi-
mum Btu/Hr the space can support, the space
is an unconfined space. You will need no ad
-
ditional fresh air ventilation.
40,000
33,000
73,000