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NOTE: SOME AREAS IN THE UNITED STATES HAVE HIGHER REQUIREMENTS
FOR CUBIC FEET PER 1000 BTU/ HOUR INPUT. (EX. CINCINNATI, OHIO CODES
REQUIRE 70 CUBIC FEET). CHECK YOUR LOCAL CODE BEFORE
INSTALLATION.
PRODUCING ADEQUATE AIR FOR
COMBUSTION AND VENTILATION
This section is for residential or manufactured (mobile) installation
“This heater shall not be installed in unusually tight construction unless provisions are adequate
for combustion and ventilation air.”
NOTE: This heater shall not be installed in a room or space unless the required volume of in-
door combustion air is provided by method in the National Fuel Gas Code, ANSIZ223.1/NFPA
54, International Fuel Gas Code, or applicable codes.
The National Fuel Gas Code, ANSI Z223.1/NFPA 54 defines unusually tight construction or
unconfined space as a space whose volume is less than 50 cubic feet per 1,000 BTU per hour
(4.8m
3
per kw) of 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 (4.8m
3
per kw) of aggregate input rating of all appliances installed in that space. Rooms
communicating directly with space in which appliances are installed, through openings not
furnished with doors, are considered a part of unconfined space.
“WARNING: IF THE AREA IN WHICH HEATER MAY BE OPERATED DOES NOT
MEET REQUIRED VOLUME FOR INDOOR COMBUSTION AIR, COMBUSTION
AND VENTILATION AIR SHALL BE PROVIDED BY ONE OF METHODS DE-
SCRIBED IN NATIONAL FUEL GAS CODE, ANSI Z223.1/NFPA 54, INTERNA-
TIONAL FUEL GAS CODE, OR APPLICABLE CODES.”
“WARNING: IF AREA IN WHICH HEATER MAY BE OPERATED IS SMALLER
THAN THAT DEFINED AS AN UNCONFINED SPACE OR IF BUILDING IS OF
UNUSUALLY TIGHT CONSTRUCTION, PROVIDE ADEQUATE AIR FOR
COMBUSTION AND VENTILATION BY ONE OF METHODS DESCRIBED IN
NATIONAL FUEL GAS CODE, ANSI Z223.1/NFPA 54 AIR FOR COMBUSTION AND
VENTILATION OR APPLICABLE LOCAL CODES.”
Unusually tight construction is defined as construction where:
a) Walls and ceilings exposed to outside atmosphere have a continuous water vapor retarder
with a rating of 1 perm (6 x 10
-11
kg per pa-sec-m
2
) or less with openings gasketed or sealed;
b) Weather stripping has been added on openable windows and doors.
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.
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