Should CO (carbon monoxide) detectors be placed like smoke detectors?
Smoke detectors are placed near or on the ceiling because both heat and smoke rise.
CO however is the same weight as air, so it mixes all over. That means that you could put your CO detectors on the ceiling, or you could put them anyplace that is convenient. This is especially useful because many of them are designed to be plugged directly into an outlet, so you can use any outlet.
If you have small children, do not put it within their reach or they sill simply unplug it. Generally speaking if you have just one in the house, put it near the bedroom. That is where you are most vulnerable because while sleeping you do not notice the symptoms of CO poisoning, like drowsiness.
Ideally you will have one on each floor of the house, and one just outside the furnace room or about 10 feet from any major fuel burning appliance.
Do not put them in drafty areas.
Do not put them in corners of rooms where the air doesn't move at all.
Do not put them in direct sunlight.
Do not put them within reach of children.
Do not put them inside the garage (they will always be going off).
If your alarm does go off and you are NOT groggy or feeling ill, call 911 or the fire department. If you are groggy, sleepy or feeling ill -- get everyone out of the house immediately and call for help from a neighbour's house or outside with your cell phone.
Remember, carbon monoxide puts you to sleep first, then kills you. Fresh air can save your life.