7
Important Vent-Piping Note: Sloped vent pipe at
least 1/4” for every 1’ to the vent terminal.
1.
Provide combustion and ventilation air in accordance
with the section “Air for Combustion and Ventilation”,
of the National Fuel Gas Code, ANSI Z223.1/NFPA 54,
or applicable provisions of the local building codes.
2.
Boiler is located in unconfi ned space in building or
conventional construction frame, masonry or metal
building, infi ltration normally is adequate to provide air
for combustion and ventilation. However, if equipment
is located in building of tight construction (See National
Fuel Gas Code, ANSI Z223.1), boiler area should be
considered as confi ned space. If there is any doubt,
install air supply provisions in accordance with latest
revision of National Fuel Gas Code.
3.
Boiler is installed in unconfi ned space, in building of
tight construction, air for combustion and ventilation
must be obtained from outdoors or from spaces freely
communicating with outdoors. Permanent opening
or openings having 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 outdoors and shall have
same cross-sectional area of openings to which they
are connected.
4.
When air for combustion and ventilation is from inside
buildings, confi ned space shall be provided with two
permanent openings, one starting 12 inches from top
and one 12 inches from bottom of enclosed space. Each
opening shall have minimum free area of 1 square inch
per one thousand (1000) Btu per hour of total input
rating of all appliances in enclosed space, but must
not be less than one hundred (100) square inches.
Openings must freely communicate directly with other
spaces of suffi cient volume so combined volume of all
spaces meets criteria for unconfi ned space. Figure 1.
5.
When boiler is installed in confi ned space and all
air is provided from outdoors confi ned space shall
be provided with one or two permanent openings
according to methods A or B (listed below). When ducts
are used, they shall be of same cross sectional area as
free area of area of openings to which they connect.
Minimum dimension of rectangular air ducts shall be
not less than 3 x 3 inches or 9 square inches.
Vent-Piping
Combustion
Air
Openings
Combustion Air supplied from
inside the building
Vent-Piping
Combustion Air
Openings with
Motorized Dampers
Combustion Air supplied from
outside the building
VENTILATION AND COMBUSTION AIR
Figure 1
Figure 2
