On the ceilings, mount the device away from corners and walls, which have dead air space nearby. About eight to 10 inches is the recommended distance. On walls, install the detectors high, because smoke rises, and place them eight to 10 inches away from corners and ceilings. Install smoke detectors at least three feet from vents, which might re-circulate the smoke. Never place smoke detectors on un-insulated walls or ceilings.
Extreme temperatures can ruin batteries and prevent smoke from reaching the detectors.
In The Home Smoke detectors provide an early warning system to allow you and your family extra time to get out of the house fast during a fire. This means having a prepared escape plan, with two possible escape routes from every room, and a prearranged meeting place outside the house. Families should actually run through a fire drill at least twice a year. They require no outlets or wiring connection, however, batteries must be replaced twice a year. We recommend you change them in the Spring and in the Fall when you change your clocks.