The most important places to put smoke alarms are inside each bedroom and outside each sleeping area according to the National Fire Protection Association. Living rooms, dens, family rooms, basements and stairways to upper levels of the house also need smoke alarms.
Smoke alarms are designed to alert home residents to the presence of smoke and fire with maximum possible time for escape. Because fire can spread much faster through a home with modern furnishings than one with older furnishings made mostly from natural materials, current NFPA standards require more smoke alarms than were recommended in the past. The NFPA also recommends monthly testing of smoke alarms as well as regular maintenance according to the manufacturer's instructions.
Since smoke rises, smoke alarms work best when mounted on ceilings or no more than 12 inches from flat ceilings. If the ceiling is peaked, the smoke alarms should be between 4 and 36 inches from the apex. NFPA standards call for smoke alarms to be located away from windows, doors and other drafts that might interfere with smoke detection and at least 10 feet away from cooking appliances to minimize false alarms. A mix of ionization smoke alarms, which are best at detecting flaming fires, and photoelectric smoke alarms for detecting smoldering fires is best.