Why does…? #11: How does a smoke alarm smell smoke?
A photoelectric alarm shines a light inside a dark chamber; smoke scatters it onto a sensor → beep (ionization alarms instead notice smoke slowing a tiny current).
How does a smoke alarm "smell" smoke? It has no nose! 🔥👃
Most home alarms are PHOTOELECTRIC: inside is a dark little chamber. A tiny infrared light shines across it — but AWAY from the light sensor, so normally the sensor sees nothing.
When smoke drifts in, the tiny smoke particles bounce some of that light sideways onto the sensor → BEEP! 🚨
The other kind is IONIZATION: a tiny source makes the air between two plates carry a very small current. Smoke particles grab the charged bits, the current drops → alarm.
Dark box, bounced light, beep! Test yours once a month, and replace it about every 10 years. ✅
Read the voiceover (transcript)
- How does a smoke alarm smell smoke? No nose!
- Inside is a dark little chamber. A light shines across it, away from the sensor.
- Smoke drifts in, and the tiny bits bounce light onto the sensor. Beep!
- Other alarms use a tiny current in the air. Smoke slows it down, and it sounds.
- Dark box, bounced light, beep!
- Next: why your screen turns off at your ear! Follow for more!
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