SOURCES
OF CARBON MONOXIDE
WHERE DOES CARBON MONOXIDE (CO)
COME FROM?
CO can be produced by appliances like a gas* or oil furnace, gas clothes dryer,
gas ranges or cook tops, gas ovens, gas-fueled water heater, wood/coal burning
stove, wood or gas fireplace, or space heater. When appliances and vents work
properly, and there is enough fresh air in your home to allow complete
combustion, the trace amounts of CO produced are typically not dangerous (all
gas appliances initially produce CO when they first start). Normally, CO is
safely vented to the outdoors. (* Gas is defined as natural gas or propane)
In multiple family dwellings where
living spaces share walls and pipes, carbon monoxide from one unit may enter a
neighboring space through floor boards, cracks, or underneath doors.
Problems arise when something goes
wrong. An appliance malfunctions; a furnace heat exchanger cracks; vents can
clog, or debris like a bird's nest can block a chimney or flue. Fireplaces,
wood-burning stoves, charcoal grills, or gas logs can produce unsafe levels of
CO if they are un-vented or not properly vented. Exhaust can seep into the home
from vehicles left running in an attached garage, even if the garage door is
open.
A sticking thermostat can keep the
furnace running constantly, depleting the oxygen supply inside the house. This
can lead to back drafting.
In some cases, problems arise even
if appliances are working properly. The following conditions are dangerous
because they can trap exhaust in your home.
Incomplete Combustion
Fuel-burning appliances need fresh air for complete burning. If several
appliances are operating at the same time in a well-insulated home, they
"compete" for the available fresh air. If this fresh air becomes low,
appliances re circulate each other's exhaust instead of venting to the outside.
Negative Indoor Air Pressure
When exhaust fans run, inside air pressure is lowered. If the indoor pressure
gets lower than the outdoor air pressure, the airflow in chimneys and vents can
reverse, pulling exhaust-containing CO back into the home.
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