Table of Contents
Advertisement
AIR FOR COMBUSTION AND VENTILATION
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
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
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 odorless passageways or ventilation
grills between them.
DETERMINING FRESH-AIR FLOW
FOR APPLIANCE 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 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 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 deter-
mine the maximum Btu/Hr the space can
support.
____________(volume of space) x 20
= (Maximum Btu/Hr the space can sup-
port)
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 appli-
ances in the space.
116412-01E
per kw) of the aggregate
3
per kw) of the ag-
3
www.desatech.com
Continued
Vent-free appliance
Gas water appliance* _______ Btu/Hr
Gas furnace
Vented gas appliance _______ Btu/Hr
Gas fireplace logs
Other gas appliances* + _______ Btu/Hr
Total
* Do not include direct-vent gas appli-
ances. Direct-vent draws combustion
air from the outdoors and vents to the
outdoors.
Example:
Gas water appliance
Vent-free appliance
Total
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
Example: 51,200 Btu/Hr (maximum the
The space in the previous example is a con-
fined 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 worksheet, adding the space
of an adjoining room. If the extra space
provides an unconfined 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
Ventilation Air From Outdoors, page 8.
C. Install a lower Btu/Hr appliance, 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.
_______ Btu/Hr
_______ Btu/Hr
_______ Btu/Hr
= _______ Btu/Hr
40,000
_______ Btu/Hr
33,000
+ _______ Btu/Hr
73,000
= _______ Btu/Hr
Btu/Hr used)
space can support)
73,000 Btu/Hr (actual amount of
Btu/Hr used)
7
Advertisement
Table of Contents
