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126875-01_G
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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 uncon-
fined 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) = 2,560 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 = (Maximum Btu/Hr the space
can support)
Example: 2,560 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.
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 40,000 Btu/Hr
Vent-free fireplace + 33,000 Btu/Hr
Total
= 73,000 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 example 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.
B.
Vent room directly to the outdoors. See Ventilation Air From
Outdoors.
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 unconfined space. You will need
no additional fresh air ventilation.
WARNING: If the area in which the heater may be
operated does not meet the required volume for indoor
combustion air, combustion and ventilation air shall
be provided by one of the methods described in the
National Fuel Gas Code, ANSI Z223.1/NFPA 54, the
International Fuel Gas Code, or applicable local codes.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining unconfined space. When
ventilating to an adjoining unconfined space, you must provide two per-
manent openings: one within 12" of the ceiling and one within 12" of the
floor on the wall connecting the two spaces (see options 1 and 2, Figure
2). You can also remove door into adjoining room (see option 3, Figure
2). Follow the National Fuel Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size of ventilation grills or ducts.
AIR FOR COMBUSTION AND VENTILATION
Continued
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or ducts. You must
provide two permanent openings: one within 12" of the ceiling and one
within 12" of the floor. Connect these items directly to the outdoors or
spaces open to the outdoors. These spaces include attics and crawl
spaces. Follow the National Fuel Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size of ventilation grills or ducts.
IMPORTANT:
Do not provide openings for inlet or outlet air into attic
if attic has a thermostat-controlled power vent. Heated air entering
the attic will activate the power vent.
Figure 3 - Ventilation Air from Outdoors
Figure 2 - Ventilation Air from Inside Building
Outlet
Air
Ventilated
Attic
Outlet
Air
Inlet
Air
Inlet Air
Ventilated
Crawl Space
To
Crawl
Space
To Attic
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
