Dozens of brands of smoke detectors are for sale in hardware, department, and discount stores. Be sure that the smoke detector you buy bears the label of an independent testing laboratory, such as UL or FM.
Several types of detectors are available. Some run on batteries, others on household current (new smoke detectors have both, usually for new construction or major remodeling). Some detect smoke using an ionization sensor; others use a photoelectric detection system. All approved smoke detectors, regardless of type, will offer adequate protection provided they are installed and maintained properly.
Ionization Smoke Detectors: These units detect the fire’s visible and invisible smoke particles. Smoke reduces the electric current within the unit, which in turn starts the alarm.
Photoelectric Smoke Detectors: These units also detect smoke particles, but only those large enough to be "seen" by the unit. The smoke blocks the path of a light beam within the detectors.
Either type of smoke detector can provide your family with an early warning of fire. There are units available that have both ionization and photoelectric detection within the smoke detector unit. These should improve detector reliability by reducing false alarms.