Every year in the United States, about 2000 people die in residential fires. A smoke alarm stands guard around the clock, and when it first senses smoke, it sounds an alarm. This often allows a family the precious, but limited, time to escape. About 2/3 of home fire deaths occur in homes with no smoke alarms or no working alarms.
Smoke alarms should be installed on every level of the home, outside sleeping areas, and inside bedrooms. In general, alarms should be placed in the center of a ceiling or, if you place them on a wall, they should be near the ceiling.
There are 2 types of smoke alarms:
Ionization - these alarms are more responsive to flaming fires. They use "ions" or electrically charged particles, to help detect smoke in the air.
Photoelectric - these alarms are more responsive to smoke or smoldering fires. They use a light beam to help detect the presence of smoke.
Whichever type of smoke alarm that you choose, it's imperative that you change the batteries twice a year and test them every month.