PAGE 3
FIGURE 1
VENTILATION & COMBUSTION AIR
WARNING:
AIR OPENINGS TO COMBUSTION AREA MUST NOT BE
OBSTRUCTED. BY FOLLOWING THE INSTRUCTIONS BELOW, ADEQUATE
COMBUSTION AIR CAN BE MAINTAINED
*
Unconfined area: A space whose volume is not less than 50 cubic feet per 1000
BTU per hour of all appliances installed in that space (cubic feet of space = height x
width x length).
**
Confined area: A space whose volume is less than 50 cubic feet per 1000 BTU per
hour of all appliances installed in that space (cubic feet of space = height x width x
length).
1. Ventilation of the boiler room must be adequate to provide sufficient air to properly
support combustion per the latest revision of the National Fuel Gas Code, ANSI Z223.1
section 5.3.
2. When a boiler is located in an unconfined space in a building or conventional construction
frame, masonry or metal building, infiltration normally is adequate to provide air for
combustion and ventilation. However, if the equipment is located in a building of unusually tight
construction (See the national Fuel Gas Code, Ansi Z223.1 section 1.7), the boiler area
should be considered as a confined space. In this case air for combustion and ventilation shall
be provided according to part 5 on page 4. If there is any doubt, install air supply provisions
in accordance with the latest revision of the National Fuel Gas Code.
3. When a boiler is installed in an unconfined
space, in a building of unusually tight
construction, air for combustion and ventilation
must be obtained from outdoors or from
spaces freely communicating with the
outdoors. A permanent opening or openings
having a total free area of not less than 1
square inch per 5,000 BTU per hour of total
input rating of all appliances shall be provided.
Ducts may be used to convey makeup air
from the outdoors and shall have the same
cross-sectional area of the openings to which
they are connected.
4. When air for combustion and ventilation
is from inside buildings, the confined space
shall be provided with two permanent
openings, one starting 12 inches from the top
and one 12 inches from the bottom of the
enclosed space. Each opening shall have a
minimum free area of 1 square inch per one thousand (1000) BTU per hour of the total input
rating of all appliances in the enclosed space, but must not be less than one hundred (100)
square inches. These openings must freely communicate directly with other spaces of
sufficient volume so that the combined volume of all spaces meets the criteria for an
unconfined space.
