Originally Posted by MedicShawn

PLACEMENT OF CARBON MONOXIDE DETECTORS IMPORTANT

Proper placement of a carbon monoxide detector is important. If you are installing only one carbon monoxide detector, the Consumer Product Safety Commission (CPSC) recommends it be located near the sleeping area, where it can wake you if you are asleep. Additional detectors on every level and in every bedroom of a home provides extra protection.

Homeowners should remember not to install carbon monoxide detectors directly above or beside fuel-burning appliances, as appliances may emit a small amount of carbon monoxide upon start-up. A detector should not be placed within fifteen feet of heating or cooking appliances or in or near very humid areas such as bathrooms.

When considering where to place a carbon monoxide detector, keep in mind that although carbon monoxide is roughly the same weight as air (carbon monoxide's specific gravity is 0.9657, as stated by the EPA; the National Resource Council lists the specific gravity of air as one), it may be contained in warm air coming from combustion appliances such as home heating equipment. If this is the case, carbon monoxide will rise with the warmer air.

For this reason, the makers of First Alert (R), the leading brand in carbon monoxide detector technology, suggests mounting the detector on the ceiling. This also puts the detector out of the way of potential interference, such as pets or curious children.


From http://www.homesafe.com/coalert/detect.htm