Book 3, Question 99
Why Do Smoke Alarms Beep?
A smoke alarm is a tiny lookout. It watches the air in a room, and shouts a loud beep if smoke particles show that a fire may have started. Many alarms shine a small light across a dark chamber.
From the book
Page from A Million Whys Book 3
More fun facts
- Smoke alarms detect fires by sensing tiny particles in the air.
- In some alarms, smoke particles lower a tiny electric current inside a chamber, and that sets off the alarm.
- Having working smoke alarms at home cuts the risk of dying in a house fire by 55 percent.
- A newer U.S. standard requires smoke alarms to be more sensitive to all kinds of fires and to give fewer false alarms from cooking.
- Scientists at NIST test smoke alarms in a kitchen fire lab, and even newer alarms can still go off when bacon is cooking.
Questions kids ask
Why does my smoke alarm go off when we cook?
Cooking can send tiny particles into the air, and smoke alarms sense particles. Newer alarms are designed to have fewer of these false alarms.