Smoke detectors save lives, prevent injuries and minimize property damage. The risk of dying from fire is twice as high in homes that do not have functioning detectors. Smoke detectors work by sensing the rising smoke from a fire and sounding a piercing alarm. This sets up an electric current within the detector chamber. When smoke enters the chamber, it attaches itself to the ions and reduces the flow of electric current, thus setting off an alarm.
Photoelectric detectors sound when the smoke is dense enough to deflect a beam of light.
Smoke detectors also differ by power source. The batteries in battery-powered smoke detectors last approximately one year. Some will keep this up for a week or longer. Smoke detectors that operate on household electric current operate as long as there is current in the circuit to which they are connected. They are, therefore, vulnerable to power failure.