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5
AIR FOR COMBUSTION AND VENTILATION
WARNING: This heater
shall not be installed in a confined
space or unusually tight con-
struction unless provisions are
provided for adequate combus-
tion and ventilation air. Read the
following instructions to insure
proper fresh air for this and other
fuel-burning appliances in your
home.
PROVIDING ADEQUATE
VENTILATION
The following are excerpts from National
Fuel Gas Code, NFPA 54/ANSI Z223.
1, Section 5.3, Air for Combustion and
Ventilation.
All spaces in homes fall into one of
the three following ventilation
classifications:
1. Unusually Tight Construction
2. Unconfined Space
3. Confined Space
The information on pages 5 through 6
will help you classify your space and
provide adequate ventilation.
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 unconfined space as a space whose
volume is not less than 50 cubic feet
per 1,000 Btu per hour (4.8 m
3
per kw)
of the aggregate input rating of all ap-
pliances 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.
This heater shall not be installed in a
confined space or unusually tight con-
struction unless provisions are pro-
vided for adequate combustion and
ventilation air.
* Adjoining rooms are communicat-
ing only if there are doorless passage-
ways or ventilation grills between them.
DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION
Determining if You Have a Confined or Unconfined Space
Use this worksheet 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×width×height).
Length×Width×Height= cu.ft. (volume of space)
Example: Space size 20ft. (length)×16ft.(width)×8ft. (ceiling height)=2560cu. 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. Divide the space volume by 50 cubic feet to determine the maximum Btu/Hr the space can support.
(volume of space)÷50 cu. ft.=(Maximum Btu/Hr the space can support)
Example: 2560 cu. ft. (volume of space)÷50 cu.ft.=51.2 or 51,200(maximum Btu/Hr the space can support)
Unusually Tight Construction
The air that leaks around doors and
windows may provide enough fresh air
for combustion and ventilation.
However, in buildings of unusually tight
construction, you must provide addi-
tional fresh air.
Unusually tight construction is defined
as construction where:
a) Walls and ceilings exposed to the
outside atmosphere have a continu-
ous water vapor retarder with a rat-
ing of one perm (6×10
-11
kg per pa-
sec-m
2
) or less with openings
gasketed or sealed and
b) Weather stripping has been added
on openable windows and doors
and
c) Caulking or sealants are applied to
areas such as joints around window
and door frames, between sole
plates and floors, between wall ceil-
ing joints, between wall panels, at
penetrations for plumbing,
electrical, and gas lines, and at other
openings.
If your home meets all of the three cri-
teria above, you must provide additional
fresh air. See Ventilation Air From
Outdoors.
If your home does not meet all of the
three criteria above, proceed to Deter-
mining Fresh-Air Flow For Heater
Location.