12
11
ALL AIR FROM OUTDOORS
The confined space shall be provided with two permanent openings, one commencing within 12 inches of the top and one commencing within 12
inches of the bottom of the enclosure. The openings shall communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely
communicate with the outdoors.
When directly communicating with the outdoors each opening shall have a minimum free area of 1 square inch per 4,000 BTU oer hour of total
input rating of all equipment in the enclosure. (Figure 7)
When communicating with the outdoors through vertical ducts, each opening shall have a minimum free area of 1 square inch per 4,000 BTU per
hour of total input rating of all equipment in the enclosure. (Figure 8)
1. When communicating with the outdoors through horizontal ducts, each duct openin shall have a minimum free area of 1 square inch per 2,000
BTU per hour of total input rating of all equipment in the enclosure. (figure9)
When ducts are used, they shall be of the same cross-sectional area as the free area of the openings to which the connect. The minimum dimension
of the rectangular air ducts shall not be less than 3 inches. For other combustion and ventilation air openings, refer to the National Fuel Gas Code
ANSI Z223.I.*
Figure 7
Figure 8
AIR SUPPLY
Important air for combustion and ventilation must not come from a corrosive atmosphere. Any failure due to corrosive elements in the atmosphere
is excluded from warranty coverage.
The following types of installation ( not limited to the following) will require outdoor air for combustion due to chemical exposure and may reduce
but not elminate the presence of corrosive chemicals in the air.
. Beauty shops.
. Photo processing labs.
. Buildings with indoor pools.
. Water heaters installed in laundry, lobby or craft rooms.
. Water heaters installed in chemical storage areas.
Combustion air must be free of acid-forming chemicals such as sulfur, fluorine, chlorine. These elements are found in aerosol sprays, detergents,
bleaches, cleaning solvents, air fresheners, paint and varnish removers, refrigerants, and many other commercial or household products. When
urned, vapors from these products form highly corrosive acid compounds.
These products should not be stored or used near the water heater or air inlet.
Combustion and ventilation air requeriments are determinated by the location of the water heater. The water heater may be located in either an
open (unconfined) area or in a confined area or small enclosure, such as a closet or small room. Confined spaces are areas with less than 50 sq.ft.
ALL AIR FROM INSIDE THE BUILDING
The confined space shall be provided with two permanent openings communicating directly with an additional room(s) of sufficient volume so that
the combined volume of all spaces meets the criteria for an unconfined space shall be considered in making this determination. Each opening shall
have a minimum free area of 1 square inch per 1,000 BTU per hour of the total input rating of all gas utilization equipment in the confined space,
but not less than 100 square inches.
Figure 6
CHIMNEY OF GAS VENT
