7
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
PRODUCING 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 as 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 unconfining
space as a space whose volume is not 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. 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 should 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 (6x10
-11
kg per pa-sec-m
2
) or less with openings
gasketed or sealed and
b) weather stripping has been added on windows that can be opened 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”.
