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200020-01A
WATER VAPOR: A BY-PRODUCT OF
UNVENTED ROOM HEATERS
Water vapor is a by-product of gas combus-
tion. An unvented room heater produces ap-
proximately one (1) ounce (30 mL) of water
for every 1,000 BTUs (0.3 KWs) of gas input
per hour. Unvented room heaters are recom-
mended as supplemental heat (a room) rather
than a primary heat source (an entire house).
In most supplemental heat applications, the
water vapor does not create a problem. In
most applications, the water vapor enhances
the low humidity atmosphere experienced
during cold weather.
The following steps will help ensure that water
vapor does not become a problem.
1. Be sure the heater is sized properly for the
application, including ample combustion
air and circulation air.
2. If high humidity is experienced, a dehu-
midifier may be used to help lower the
water vapor content of the air.
3. Do not use an unvented room heater as
the primary heat source.
AIR FOR COMBUSTION AND VENTILATION
WARNING: This heater shall
not be installed in a confined
space or unusually tight construc-
tion unless provisions are provid-
ed for adequate combustion and
ventilation air. Read the following
instructions to insure proper fresh
air for this and other fuel-burning
appliances in your home.
Today’s homes are built more energy efficient
than ever. New materials, increased insulation
and new construction methods help reduce
heat loss in homes. Home owners weather
strip and caulk around windows and doors
to keep the cold air out and the warm air in.
During heating months, home owners want
their homes as airtight as possible.
While it is good to make your home energy
efficient, your home needs to breathe. Fresh
air must enter your home. All fuel-burning ap-
pliances need fresh air for proper combustion
and ventilation.
Exhaust fans, fireplaces, clothes dryers and
fuel burning appliances draw air from the house
to operate. You must provide adequate fresh
air for these appliances. This will insure proper
venting of vented fuel-burning appliances.
PROVIDING ADEQUATE VENTILATION
The following are excerpts from
National Fuel
Gas Code, ANSI Z223.1/NFPA 54, 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 7 through 9 will help
you classify your space and provide adequate
ventilation.
