We sometimes get calls from people worried about radiation from smoke detectors in their homes. There are many reasons why the public need not fear these products.
Ionization chamber smoke detectors contain very small amounts of nuclear material. They might use americium-241, radium-226 or nickel-63. These products detect fires early and can save lives. [We explained how smoke detectors work in greater detail in an earlier blog post.]
The Atomic Energy Commission granted the first license to distribute smoke detectors in 1963. These early models were used mainly in factories, public buildings and warehouses. In 1969, the AEC allowed homeowners to use smoke detectors without the need for a license. Their use in homes expanded in the early 1970s. The NRC took over from the AEC in 1975.
Makers and distributors of smoke detectors must get a license from the NRC. They must show that the smoke detector meets our health, safety and labeling requirements.
Most smoke detectors sold today use 1 microcurie or less of Am-241. They are very safe. A 2001 study found people living in a home with two of these units receive less than 0.002 millirems of radiation dose each year. That is about the dose from space and the earth that an East Coast resident receives in 12 hours. Denver residents receive that dose in about three hours. These doses are part of what is known as “background radiation.”
The radioactive source in the smoke detector is between two layers of metal and sealed inside the ionization chamber. The seal can only be broken by the deliberate use of force, which obviously we discourage. Still, even then it would result in only a small radiation dose. The foil does not break down over time. In a fire, the source would release less than 0.1 percent of its radioactivity. It’s important to understand that none of the sources used in smoke detectors can make anything else radioactive.
What about disposing of smoke detectors? A 1979 analysis looked at the annual dose from normal use and disposal of Am-241 smoke detectors. The study used actual data and assumptions that would overstate the risk. It allowed the NRC to conclude that 10 million unwanted smoke detectors each year can be safely put in the trash.
The 2001 study looked at doses from misuse. It found that a teacher who removed an americium source from a smoke detector and stored it in the classroom could receive 0.009 millirems per year. If the teacher used the source in classroom demonstrations, handling it for 10 hours each year would give less than a 0.001 mrem dose. A person who swallowed the source would receive a 600 mrem dose while it was passing through the body.
I hope this information allays concerns. Unless you remove and swallow the source, your dose from a smoke detector could not be distinguished from what you get throughout your day. And that smoke detector could save your life.
U.S. NRC Blog 
Because it is very important, make sure it works continuously. Choose detector with dual power, to keep your safety
bottom line is fire alarms save lives. The negatives are very little to non.
This is quite an interesting article, I never thought of the nuclear materials that are made to build smoke alarms. Im sure its not harmful but another thing I have learned today. Thanks for the post
See this site about smoke detectors
http://www.saskwastereduction.ca/recycle/resources/smoke-detectors/smoke-detectors
I would be surprised if less then 90% of detectors were thrown in home garbage as well batteries.
Laws with out punishment do not work well.
Information on proper disposal can be found here: http://www.epa.gov/radiation/sources/smoke_dispose.html
Moderator
how to dispose off the Smoke detector (radio active type) when it become faulty
Yes, I agree that smoke alarm save life and its good to use it in our home. Thanks for sharing this valuable information!!!
So then it is safe to work 20 feet from 200 detectors for 20 years, I sold fire alarm systems for commercial buildings and have been close to many detectors 20 feet or so. A note, to do a quick test of ionization detectors, at 20 feet with low air movement blow across a lit end of a cigarette towards a detector and with in a minute or so it will alarm, the farthest distance I have done is 30 feet with 20 foot ceilings. The ambers from the cigarette easley set off the detectors. .
The ionization chamber and metal enclosure do indeed shield the majority of alpha particles coming from the radiation source. Most additional alpha particles are blocked by the plastic housing. The radiation dose from an ionizing smoke detector is almost entirely from the gamma radiation that the radioactive source emits. As the blog post notes, however, the dose is so small that it cannot be distinguished from background.
Maureen Conley
“We” all know sieverts? Not necessarily so. How many liters of gasoline did you put in your car yesterday?
Every smoke detector I’ve ever seen has its ionization chamber inside a metal enclosure. Does that shield some/most/all of the emitted radiation? I mean, relative to the 2001 study and other safety assessments.
US units are still in Rem, and last I saw, the NRC said they had no plans to move to Sv. I’m in the US and I would trust Rem more than Sv, (even though they are technically the same thing), but that’s just training/experience/exposure to it.
The 1979 analysis expressed results in terms of mrem only. The 2001 study expressed doses both in mrem and millisieverts. To keep the units of measure consistent, this blog post expresses dose in terms of mrem. The numbers are also more easily expressed as mrem, since 0.002 mrem is equal to 2×10 -5 mSv.
Maureen Conley
Yes, there are optical smoke detectors that do not rely on radioactive material. Those smoke detectors are more effective at quickly detecting smoldering/smoky fires while the ionizing smoke detectors (those containing radioactive material) are more effective at quickly detecting fires that proceed quickly to flame without as much smoke. Because each type of detector is more effective in certain situations, many fire experts recommend they be used in combination with each other along with carbon monoxide detectors.
Maureen Conley
The 2001 study I mentioned also looked at the doses that people involved in distribution and sales would receive from handling smoke detectors. Stockhandlers who move large numbers of cartons of packaged smoke detectors and people who work near stored cartons would receive about the same dose as the homeowner—0.002 mrem over the course of a year.
Maureen Conley
I see…so its like eating a banana or flying on a plane.
Aren’t there other technologies that can effectively detect smoke without using a radioactive material?
Why don’t you quote Sv?
We all know sieverts
Confusion by quoting Rem exasperates the misunderstanding and mistrust of nuclear data.
How about the storage of detectors like electrical wholesalers have about 200 in one area stacked up with work stations 20 feet away, would be common.