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119315-01D 7
The air that leaks around doors and windows
may provide enough fresh air for combus-
tion and ventilation. However, in buildings of
unusually tight construction, you must provide
additional fresh air.
construction where:
-
2
and
and
If your home meets all of these three
Ventilation Air From
Outdoors
If your home does not meet all of the
Deter-
mining Fresh-Air Flow For Fireplace
Location
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54 defines a confined space as a
space whose volume is less than 50 ft
3
per
1,000 Btu/hr (4.8 m
3
/kw) of the aggregate
input rating of all appliances installed in that
space and an unconned space as a space
whose volume is not less than 50 ft
3
per
1,000 Btu/hr (4.8 m
3
/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
unconned space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
AIR FOR COMBUSTION
AND VENTILATION
Continued
DETERMINING FRESH-AIR FLOW
Use this work sheet to determine if you have
a conned or unconned space.
Includes the room in which you will install
replace plus any adjoining rooms with door-
less 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 16 ft. (length) x 14 ft.
(width) x 8 ft. (ceiling height) = 1792 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 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 replace _________ Btu/Hr
Gas water heater* _________ Btu/Hr
Gas furnace _________ Btu/Hr
Vented gas heater _________Btu/Hr
Gas replace logs _________ Btu/Hr
Other gas appliances* + _________ 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 replace + _________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: 35,840 Btu/Hr (maximum the
space can support)
40,000 Btu/Hr (actual amount of
Btu/Hr used)
30,000
10,000
40,000