In addition to outside every bedroom, if you sleep with the bedroom door shut, place additional alarms in the bedroom so they will sound loud enough to wake a sleeping person. New homes require smoke detectors in every bedroom and hard-wired alarms so that if one goes off they all sound. If a hearing-impaired person resides in the home, get a smoke detector for the bedroom that flashes bright light instead of sounding an alarm. Place the unit where the light will shine on the person sleeping. These alarms work best hard-wired, since battery versions may not flash bright enough to wake a sleeping person.
On a floor without bedrooms, a smoke detector should be placed outside the living or family room. Don't forget the basement, it has furnaces, water heaters and other equipment that could pose fire hazards. Put the basement detector on the ceiling of the basement at the bottom of the stairs. In a two-story home, locate a detector at the bottom of the staircase that leads to the second floor.
Some areas in the home should not have smoke detectors installed. An detector in a kitchen would likely sound an alarm every time someone cooked. Smoke detectors don't do well in garages because car exhaust will set them off. You don't want to have so many nuisance alarms that the sound of a smoke detector becomes commonplace and not cause for alarm. Unheated attics have extreme temperatures that prevent smoke detectors from working. Bathrooms typically have too much steam for a smoke detector to work well.
Plan placement of smoke detectors carefully; put them on the ceiling or high on a wall. Dead air space results when hot, turbulent air moves so much it misses areas near walls. To guard against this, detectors on the ceiling should be 4 inches from the wall. Detectors high on a wall should be 4 to 12 inches from the ceiling. In areas that have a very high ceiling, put the smoke detector near the highest point. Don't mount detectors near a door or window that could cause a draft that would carry smoke away from the detector.