Science & TechHow it works

How your smoke detector sees smoke without having an eye.

Inside sits a dark chamber with an LED and a photodiode set at an angle to each other. In clean air the light beam misses the diode. When smoke particles drift in, they scatter light sideways, the diode catches it, and the alarm sounds. The older ionisation type with radioactive americium is banned in homes in parts of Europe, such as France.

Useful: Dust and insects in the chamber trigger false alarms: vacuum it gently once a year.

Source: en.wikipedia.org

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