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About
Combustion
Combustion
Appliance Backdrafting
As
we exhaust air from our homes, and as air naturally leaks out of our homes
because of wind or the stack effect, it is replaced by outdoor air. If we
exhaust a lot of air, we can depressurize the home. Sufficient
depressurization can actually pull air and combustion products back down a
chimney or any flue, such as that of a gas water heater, and into the
house. Because of the harmful substances, such as carbon
monoxide, in
combustion gases, this depressurization can create a very dangerous
situation.
Forces
working to depressurize a home include those shown in the figure below,
bathroom exhaust fans, kitchen range hoods, and clothes dryers. Other
forces not shown in the diagram include the fireplaces, leaky return ducts
near combustion equipment, leaky supply ducts outside the conditioned
space, wind, and the stack effect (warm air rising in a building tends to
depressurize lower areas). If these forces are great enough, they can work
to suck air and combustion products back down the chimney or flue and into
the house, as shown by the red arrows in the diagram.
| Source:
Environmental Protection Agency (EPA) |
EPA Disclaimer:
The information
provided on this page is based upon the EPA's current scientific and
technical understanding of the issues presented. Following the
advice given will not necessarily provide complete protection in all
situations or against all health hazards that may be caused by
indoor air pollution and other indoor environmental contaminants.
Mention of any trade names or commercial products does not
constitute EPA endorsement or recommendation for use. |
EnTech Disclaimer:
EnTech Supply makes no claim as to the accuracy of
the information provided above, which is reprinted as a courtesy to
the reader from an EPA document. The reader should conduct their own
independent research to verify the accuracy of EPA's information. |
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