2. Combustion& VentilationAir
Poison carbon monoxide gas hazard.
Use methods described here to provide
combustion and ventilation air.
Failure to provide adequate combustion and
ventilation air can result in personal injury
and/or death.
Furnaces require ventilation openings to provide sufficient air for
proper combustion and ventilation of flue gases. All duct or open-
ings for supplying combustion and ventilation air must comply
with the gas and electrical codes, or in the absence of local codes,
the applicable national codes.
When the installation is complete, check that all appliances have
adequate combustion air and are venting properly. See Venting
And Combustion Air Check in this manual.
ContaminatedCombustionAir
Installations in certain areas or types of structures will increase
the exposure to chemicals or Halogens which may harm the fur-
nace. These instances must use only outside air for combustion.
The following areas or types of structures may contain or have ex-
posure to the substances listed below. The installation must be
evaluated carefully as it may be necessary to provide outside air
for combustion.
• Commercial buildings.
• Buildings with indoor pools.
• Furnaces installed in laundry rooms.
• Furnaces installed in hobby or craft rooms.
• Furnaces installed near chemical storage areas.
• Permanent wave solutions for hair.
• Chlorinated waxes and cleaners.
• Chlorine based swimming pool chemicals.
• Water softening chemicals.
• De-icing salts or chemicals.
• Carbon tetrachloride.
• Halogen type refrigerants.
• Cleaning solvents (such as perchloroethylene).
• Printing inks, paint removers, varnishes, etc..
• Hydrochloric acid.
• Sulfuric Acid.
• Solvent cements and glues.
• Antistatic fabric softeners for clothes dryers.
• Masonry acid washing materials.
Confined Space Installation
NOTE: A confined space is defined as an area with less than 50
cubic feet(1.4m s) per 1,000 BTUH input rating for all gas ap-
pliances installed in the area.
Air Openings and Connecting Ducts
1. Total input rating for all gas appliances MUST be consid-
ered when determining free area of openings.
2. Connect ducts or openings directly to outside.
3. When screens are used to cover openings, they MUST be
no less than 1/4" (6ram) mesh.
4. The minimum dimension of rectangular air ducts MUST
NOT be less than 3" (75mm).
5. When sizing grille or louver, use the free area of opening. If
free area is NOT stamped or marked on grill or louver, as-
sume a 20% free area for wood and 60% for metal.
Requirements
1. Provide confined space with sufficient air for proper com-
bustion and ventilation of flue gases using horizontal or ver-
tical ducts or openings.
2. Figure 3 illustrates howto provide combustion and ventila-
tion air. A minimum of two permanent openings, one inlet
and one outlet, are required.
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