4.1 Possible causes of CO formation
The following conditions can result in transient CO situations in the
home:
a) Reverse venting of fuel burning appliances caused by:
- Outdoor ambient conditions such as wind direction and/or velocity,
including high gusts of wind; heavy air in the vent pipes (cold/humid
air with extended periods between cycles).
- Negative pressure differential resulting from the use of exhaust
fans.
- Simultaneous operation of several fuel burning appliances compe-
ting for limited internal air.
- Vent pipe connection vibrating loose from clothes dryers, furnaces,
or water heaters.
- Obstructions in or unconventional vent pipe designs which amplify
the above situations.
b) Extended operation of unvented fuel burning devices (range, oven,
fireplace, etc.).
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