77
AIR FOR COMBUSTION AND 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.
Providing Adequate 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 7 through 9 will help you classify your space and provide adequate ventilation.
Confined and Unconfined Space
A
confined space is a space whose volume is less than 50 cu. ft. per 1,000 BTU/hr (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/hr (4.8 m^3 per kw) of the aggregate input rating of all appliances installed in that space.
Rooms connecting directly with the space in which the appliances are installed*, through openings not furnished with
doors, are considered a part of the unconfined space.
This heater shall not be installed in a confined space or unusually tight construction unless provisions are provided for
adequate combustion and ventilation air.
* Adjoining rooms are connecting only if there are doorless passageways or ventilation grills between them.
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 additional fresh air.
Unusually tight construction is defined as construction where:
a) Walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating 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 on 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 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 9). If your home does not meet all of the three criteria above, proceed to “Determining Fresh-Air Flow
For Heater Location”
.
