A smoke detector is a device that senses smoke, which can alert you to a fire and give some time to leave the area. Smoke detectors normally generate an audible alarm and it’s a device in itself which can be wired into any electrical point with a battery backup or just with a battery.
There are mainly two types of smoke detectors; ionization and photoelectric.
An ionization smoke detector uses a radioisotope to detect the difference in air and generates the alarm. These are sensitive to the flaming stage of fire.