Filter
Top Products
COMBUSTION AND VENTILATION AIR
When installed, this gas appliance must be provided with fresh
air for combustion, ventilation, and dilution of hot flue gases.
The minimum required volume of the area where the appliance is
installed should be 50 cubic feet per 1,000 btu/hr.
If installed in an area of the home that is considered an unconfined
space, the natural infiltration of air around windows and doors
will be adequate. If the area is considered a confined space (less
than 50 cubic feet per 1,000 btu), fresh air can be supplied by
providing two permanent openings into adjoining rooms. Each
opening shall have a minimum free area of one square inch per
1,000 btu per hour of the total input rating of all gas appliances in
the confined space, but not less than 100 square inches. One of
the openings shall be within 12 inches of the ceiling and one
within 12 inches of the floor. See Figure A.
If the home is of unusually tight construction (new and remodeled
homes), free air must be supplied through opening(s) to the
outdoors. This can be accomplished by providing 2 permanent
openings, one commencing within 12 inches of the ceiling and
one within 12 inches of the floor. These openings shall
communicate directly with the outdoors, or spaces that
communicate freely with the outdoors, such as a ventilated attic
and crawl space through galvanized or equivalent corrosion-
resistant ducts. Exception: unobstructed stud and joist spaces
are acceptable ducts provided that not more than one fire block
is removed. Special provisions must be taken to insure that
these stud and joist spaces cannot be blocked with insulation or
other objects. Each of these openings using vertical ducts shall
have a minimum free area of one square inch per 4,000 btu/hr of
total input rating of all gas appliances. See Figure B and C. If
horizontal ducts are used, the minimum free area shall be one
square inch per 2,000 btu/hr of total input rating of all gas
appliances.
Fresh make-up air can also be provided through a duct to one
permanent opening commencing within 12 inches of the ceiling.
The minimum free area of this opening shall be one square inch
per 3,000 btu/hr of the total input rating of all gas appliances but
not less than the sum of the areas of all vent connectors in the
space. See Figure D.
When calculating the amount of fresh air needed you must include
make-up air requirements for the operation of exhaust fans, kitchen
ventilation systems, clothes dryers, and fireplaces.
Additional information can be found in the latest edition of ANSI
Z223.1 (National Fuel Gas Code).
ALL COMBUSTION AIR FROM ADJACENT INDOOR
SPACES THROUGH INDOOR COMBUSTION AIR
OPENINGS
ALL COMBUSTION AIR FROM OUTDOORS, INLET
AIR FROM VENTILATED CRAWL SPACE AND
OUTLET AIR TO VENTILATED ATTIC
ALL COMBUSTION AIR FROM OUTDOORS
THROUGH VENTILATED ATTIC
ALL COMBUSTION AIR FROM OUTDOORS
THROUGH SINGLE COMBUSTION AIR OPENING
UL Listed Vent Cap
UL Listed Gas Vent
Opening
Opening
UL Listed Vent Cap
UL Listed Vent Cap
UL Listed Vent Cap
UL Listed Gas Vent
UL Listed Gas Vent
UL Listed Gas Vent
Ventilation Louvers (each
end of attic)
Outlet Air
Inlet Air
Ventilation Louvers for unheated crawl space
Ventilation Louvers (each
end of attic)
Outlet Air
Inlet Air Duct (ends 1 ft.
[300mm] above floor)
Opening
Alternate Opening
Location
F
I
G
U
R
E
A
F
I
G
U
R
E
B
F
I
G
U
R
E
D
F
I
G
U
R
E
C
Page 5
Inlet
Grille
Inlet
Grille