How does a smoke detector work?

A smoke detector works by detecting the presence of smoke particles in the air, indicating the possibility of a fire. There are primarily two types of smoke detectors: ionization smoke detectors and photoelectric smoke detectors. Here’s how each type works:

Ionization Smoke Detector:

Inside an ionization smoke detector, there are two charged plates and a small amount of radioactive material, typically americium-241.
The radioactive material emits alpha particles, which ionize the air between the plates, creating a small electric current.
When smoke enters the detector chamber, it disrupts the ionization process by attaching to the ions and particles in the air.
This disruption reduces the electric current flow between the plates, triggering the alarm.
Ionization smoke detectors are particularly sensitive to fast-burning, flaming fires.
Photoelectric Smoke Detector:

Photoelectric smoke detectors contain a light source (typically an LED) and a light-sensitive sensor, positioned at an angle to each other within a chamber.
When smoke enters the chamber, it scatters light from the light source, causing some of the scattered light to fall onto the light-sensitive sensor.
This change in light intensity triggers the alarm.
Photoelectric smoke detectors are more sensitive to slow, smoldering fires.
In both types of smoke detectors, when the alarm is triggered, a loud audible alarm is activated to alert occupants of the presence of smoke, allowing them to take necessary actions such as evacuating the premises and contacting emergency services.