Carbon monoxide (CO) is slightly lighter than air and can also be carried by warm rising air, so detectors should be installed about 5 feet (1.5 m) above the floor on a wall. They may also be mounted on the ceiling.
Do not install the detector directly beside or above fireplaces, stoves, boilers, or other flame-producing appliances. Keep it out of reach of children and pets.
Install one detector on each floor of the building. If only one unit is used, place it close to sleeping areas and ensure the alarm is loud enough to wake occupants.