pictured … Smoke detector 1: Optical chamber with labyrinth 2: Cover 3: Case molding 4: Photo diode 5: Infrared LED
All smoke detectors consist of just two basic parts
- a sensor to detect smoke and
- a loud horn to alert people to the presence of smoke.
Most smoke detectors operate using either a 9-volt battery or 120-volt electrical house current. There are two main types of smoke detector sensors.
- Photoelectric detectors use beams of light or low-powered lasers. In the event of a fire that generates sufficient smoke, these light beams would be blocked, triggering an alarm. Photoelectric detectors tend to be larger and aren’t very sensitive.
- Ionization detectors use an ionization chamber and a source of ionizing radiation to detect smoke. Compared to photoelectric detectors, ionization detectors are much more sensitive, smaller, and cheaper. As a result, they’re also much more common in homes.