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AIR FOR COMBUSTION AND
VENTILATION
Continued
c. caulking or sealants are applied to areas such as
joints around window and door frames, between sole
plates and floors, between wall-ceiling joints, between
wall panels, at penetrations for plumbing, electrical,
and gas lines, and at other openings.
If your home meets all of the three criteria above, you
must provide additional fresh air. See Ventilation Air
From Outdoors , page 6 .
If your home does not meet all of the three criteria above,
proceed to Determining Fresh-Air Flow For Fireplace
Location, below .
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1 defines a confined space
as a space whose volume 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 unconfining space as a space whose
volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8 m
per kw) of the aggregate 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 unconfined space.
* Adjoining rooms are communicating only if there are doorless
passageways or ventilation grills between them.
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 heater 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 open-
ings, 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: 2560 cu. ft. (volume of space) x 20 = 51,200 (maximum
Btu/Hr the space can support)
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AIR FOR COMBUSTION AND VENTILATION
Providing Adequate Ventilation (Cont.)
Determining Fresh-Air Flow For Heater Location
3.
Add the Btu/Hr of all fuel burning appliances in the space.
Vent-free heater
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas appliances* + _____________ Btu/Hr
Total
* Do not include direct-vent gas appliances. Direct-vent draws com-
bustion air from the outdoors and vents to the outdoors.
Example:
Gas water heater
Vent-free heater
Total
4.
Compare the maximum Btu/Hr the space can support with the actual
amount of Btu/Hr used.
3
__________________ 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)
56,000 Btu/Hr (actual amount of Btu/Hr used)
The space in the example above is a confined 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 6.
B.
Vent room directly to the outdoors. See Ventilation Air From Out-
doors, page 6.
C.
Install a lower Btu/Hr heater, 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
operated is smaller than that defined as an uncon-
fined space or if the building is of unusually tight
construction, provide adequate combustion and ven-
tilation air by one of the methods described in the
National Fuel Gas Code, ANSI Z223.1/NFPA 54 Sec-
tion 5.3 or applicable local codes.
_____________ Btu/Hr
_____________ Btu/Hr
_____________ Btu/Hr
_____________ Btu/Hr
_____________ Btu/Hr
= _____________ Btu/Hr
30,000
_____________ Btu/Hr
26,000
+ _____________ Btu/Hr
56,000
= _____________ Btu/Hr
5 5
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