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Friendly Reminder That Your Smoke Detector Is Totally Radioactive

Don't worry, it's supposed to be.

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Fun fact: The same group that figured out how to make the atom bomb also paved the way for the invention of the modern smoke detector.

A typical ionization smoke detector

A typical ionization smoke detector

Billboard outside one of the facilities involved with the Manhattan Project

Billboard outside one of the facilities involved with the Manhattan Project

It's true. While the physicists of the highly-secretive Manhattan Project were trying to figure out what Plutonium was all about, they created an element new to science called Americium-241 by bombarding the Plutonium with neutrons. They kept it secret for years, but eventually it found its way into our homes.

The most common type of smoke detector around today—an ionization chamber smoke detector—uses this human-created radioactive element to sense smoke and save your life in the event of a fire.

Whitepaw / Via

Americium-241 emits alpha radiation, which can cause the molecules in the air near it to gain a charge—this is key.

This radiation strips off electrons and gives some of the air molecules a charge, which completes a circuit that smoke is really good at breaking.

Alex Kasprak for BuzzFeed

Most ionization smoke detectors have a chamber filled with a small bit of Americium-241, which charges the air molecules in-between two charged plates. When the air is charged, a current powered by a battery can easily pass through that small bit of air.

When smoke enters that same bit of air, though, it bonds with the charged ions in the air, neutralizing the charge and reducing the current. When the current drops, the alarm goes off!

Don't fucking panic, though! Alpha radiation is pathetic at penetrating anything, including your skin.

USA Network / Via

The plastic around a smoke detector is generally more than enough to block that alpha radiation. Sure, Americium also releases some gamma radiation, but it is 100 times less than what is already in the environment naturally.

Science Writer, Fossil Beastmaster

Contact Alex Kasprak at

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