Check for proper burner flame performance. Flame should
extend directly outward from burners without curling, floating
or lifting off.
To avoid property damage, personal injury or death,
sufficient fresh air for proper combustion and ventilation
of flue gases must be supplied. Most homes require
outside air be supplied into the furnace area.
Improved construction and additional insulation in homes have
reduced the heat loss and made these homes much tighter
around doors and windows so that air infiltration is minimal. This
creates a problem to supply ventilation and/or combustion air for
gas-fired or other fuel burning appliances. Any use of appliances
that pull air out of the house (clothes dryers, exhaust fans,
fireplaces, water heaters, nondirect vent furnaces, etc.) could
reduce combustion air to the furnace.
If fuel-burning appliances are starved for air, the flue gases which
these appliances produce as they operate may not vent outdoors
properly, but remain in the home instead. These flue gases may
include carbon monoxide.
CARBON MONOXIDE POISONING HAZARD
Special Warning for Installation of Furnace or Air Handling
Units in Enclosed Areas such as Garages, Utility Rooms or
Carbon monoxide producing devices (such as an
automobile, space heater, gas water heater, etc.) should
not be operated in enclosed areas such as unventilated
garages, utility rooms or parking areas because of the
danger of carbon monoxide (CO) poisoning resulting from
the exhaust emissions. If a furnace or air handler is
installed in an enclosed area such as a garage, utility room
or parking area and a carbon monoxide producing device is
operated therein, there must be adequate, direct outside
This ventilation is necessary to avoid the danger of CO
poisoning which can occur if a carbon monoxide producing
device continues to operate in the enclosed area. Carbon
monoxide emissions can be (re)circulated throughout the
structure if the furnace or air handler is operating in any
CO can cause serious illness including permanent brain
damage or death.
Carbon monoxide or "CO" is a colorless and odorless gas
produced when fuel is not burned completely or when the flame
does not receive sufficient oxygen.
Be aware of these air starvation signals which indicate conditions
that may result in carbon monoxide or that carbon monoxide may
Headaches, nausea, dizziness, flu-like symptoms.
Excessive humidity, heavily frosted windows or a moist
"clammy" feeling in the home.
Smoke from a fireplace will not draw up the chimney.
Flue gases that will not draw up the appliance vent pipe.
The air for combustion and ventilation can typically be obtained
from the surrounding unconfined space or louvered closet door,
where local codes permit. Observe the following precautions
concerning air availability:
When a furnace is installed in a closet and the closet door is
louvered, do not obstruct louvers. Louvers must be open and
clear to provide combustion air to the furnace.
When a furnace is installed in a confined space within a home
and the air for combustion and ventilation enters the space
through ducts from the outside, be sure to routinely check the
entering and outlet grilled openings to verify that they are
always clear and clean.
Do not partition off a small area around the furnace utilizing a
non-louvered door. This could obstruct the combustion air
from reaching the furnace.
Relative humidity is the amount of water vapor in the air relative
to the amount the air can hold at the same temperature. The
colder the air, the less moisture it can hold. As air is warmed, its
ability to hold moisture is increased. Relative humidity is
important to your health and home as proper humidification helps
reduce respiratory difficulties and helps improve the indoor air
A good relative humidity is one just high enough to barely start
condensation along the lower edges or lower corners of the
windows. More than that can be damaging.
Frequent fogging or excessive condensation on inside windows
indicates the indoor humidity level is too high for outdoor weather
conditions. Damage to the building may result if the condition
persists. Condensation on the inside of storm windows indicates
loose inside windows. Adding weatherstripping to tighten inside
windows usually corrects this problem.
The following table shows the recommended maximum indoor
humidity in relation to the outdoor temperatures.