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PART 6: AIR REQUIREMENTS
For safe operation, an ample supply of air must be provided for proper combustion and ventilation in
accordance with Section 5.3 of the National Fuel Gas Code, NFPA-54/ANSI Z223.1 or applicable
provisions of local building codes. An insufficient supply of air will result in a yellow, luminous burner
flame, causing sooting of the heat exchanger and creating a risk of asphyxiation.
A. UNCONFINED SPACE
In buildings of conventional frame, brick or stone construction, unconfined spaces may provide adequate
air for combustion.
If the unconfined space is within a building of tight construction (buildings using the following: weather
stripping, heavy insulation, caulking, vapor barrier, etc.), air for combustion and ventilation must be
obtained from outdoors or spaces freely communicating with the outdoors. The installation instructions for
confined spaces in tightly constructed buildings must be followed to ensure adequate air supply.
B. CONFINED SPACE
When drawing combustion and dilution air from inside a conventionally constructed building to a confined
space, this space must be provided with two permanent openings, ONE IN OR WITHIN 12 INCHES OF
THE TOP ENCLOSURE AND ONE IN OR WITHIN 12 INCHES OF THE BOTTOM ENCLOSURE. Each
opening shall have a free air area of at least one square inch per 1000 BTU/hr of the total input of all
appliances in the enclosure, but not less than 100 square inches.
If the confined space is within a building of
tight construction, air for combustion,
ventilation and draft dilution must be obtained
from outdoors. When directly venting with the
outdoors or venting with the outdoors through
vertical ducts, two permanent openings,
located in the aforementioned manner, must
be provided. Each opening must have a free
area of not less than one square inch per
4000 Btu/hr of the total input of all appliances
in the enclosure. If horizontal ducts are used,
each opening shall have a free area of not
less than one square inch per 2000 Btu/hr of
the total input of all appliances in the
enclosure.
In the absence of local codes, refer to the
National Fire Protection Standard for Oil
Burning Equipment NFPA No. 31 (latest
edition).
Where an exhaust fan is installed in the same
room with the boiler, sufficient openings for air must be provided in the walls.
UNDERSIZED OPENINGS WILL CAUSE AIR TO BE DRAWN INTO THE ROOM THROUGH THE
CHIMNEY OR OTHER UNDESIRABLE OPENINGS, CAUSING POOR COMBUSTION. SOOTING MAY
RESULT WITH AN INCREASED RISK OF ASPHYXIATION.
Figure 2
– CO Warning Label