The Lethality of Eating Smoke Detectors

 by Alice Clarke

When I learned that up until 1972, your only option for a smoke detector was a sample of radioactive Americium-241 (241Am) in a box, I was quite surprised. When I found out that, as this remains the cheapest option, the vast majority of smoke detectors are still just glorified radioactive light fixtures, I had quite a few questions, and my search for answers led me to writing this article.

How this mechanism works is surprisingly simple: 241Am emits alpha particles, a detector detects them, but a sizable quantity will be blocked if smoke is present in the chamber. This drop in radiation is picked up by the detector, which sets off the alarm. (A more detailed explanation can be found on the US Nuclear Regulatory Commision website.)

Now despite how scary a radioactive box on the ceiling of every room in your home might sound, It’s actually almost entirely safe. The 241Am is always appropriately shielded by stainless steel foil and gold leaf, and even in the event of a fire, no radioactive contaminant will be released. While it’s true that some radiation is bound to escape, the quantities involved are entirely negligible. Due to the presence of natural actinides in the soil, you will receive a higher does of radiation from planting a bush in your garden than you will by standing directly under a smoke detector 24 hours a day, for 10 years.

But of course, the question I’m sure is on both our minds now, is how dangerous could it be? If you really, really tried, how viable is death by Smoke Detector? Now, there is (perhaps unsurprisingly) little information online about the effects of consuming 241Am, and much of it is contradictory. The following is what I have managed to scrape together; it may not be completely accurate, but I hope it is at least moderately interesting! And of course, under no circumstances should you ever disassemble any smoke detectors, and please, for the love of all things good, don’t eat anything you would find inside. This article is a bit of theoretical fun, is not meant to be taken seriously, and while more data on the practical effects of the radiation poisoning resultant from the consumption of 241Am would certainly be useful and much appreciated, that’s not the way I’d personally want it to be discovered. Thanks!

So. If you wanted to ingest a lethal quantity of radioactive material, and had infinite access to smoke detector parts, what would be your best bet? One way you could go about it would just be to swallow the source whole, however according to First Alert, a leading Smoke detector manufacturer, it would simply pass straight through you. So we’ll have to get more creative. If you were to remove the foil from the source, and grind it into powder, you’d likely have much better results. According to the CDC, 241Am, while it does not build up in one’s organs, does deposit directly onto your bones, where it can stay for decades. This of course will expose you to rather a lot of radiation, but calculating exactly how much is more complicated than you might think.

(if you want to skip the more in depth science-y bits, then go ahead to the next paragraph. All you’ll miss is me explaining how you figure out the dose of radiation one receives from a given radioactive source, and while it’s complex and interesting it might not be for everyone.) Now, the way radioactive material is measured is in Becquerels (Bq), which are equivalent to 1 decay of a nucleus per second. However, there is a separate measure for dose of radiation actually received by an organism, Grays (Gy). You convert between the two with an equation you almost certainly know: E=mc2! It’s actually relevant to something - The energy emitted is equal to the change in mass by the isotope, multiplied by the speed of light squared - and to change that to Gy, you just have to balance it by the mass of material that is absorbing this energy. Therefore, if you wanted to calculate the energy you’d receive from one atom of 239Pu, you’d start with the change in mass: since it emits one alpha particle to decay to 235U, then the change in mass would theoretically be

239 - (235 +4)

Which equals zero. However, the real masses are actually a little weirder. They don’t teach this till A level, but atomic masses aren’t measured in whole numbers all the time. The real Numbers are

239.052157 - (235.043924 + 4.002602)

Which equals 0.0005631 u of mass change! And as we know,

E=mc2

E = (0.0005631)c2

Now, we measure this kind of energy in eV, which is just an extra small measure of energy equivalent to 1.60218x10-19. We know 1 u=931.5 MeV/c2, and so E = (0.005631)(931.5 MeV/c2)(c2) = 5.25 MeV. Now, if none of that makes any sense, don’t worry, all you need to know is that we can, using this, calculate the amount of energy transferred to your body when 241Am decays! And a couple of sums, and a cross-check with Wikipedia later, we have our answer! 5.486 MeV per atom that decays.

So to scale up is very easy: as I said before, radioactive material is measured in Bq, which are decays/sec, and we know how much energy one atom decaying gives out. And as there is on average 33000 Bq of 241Am in every smoke detector, that much 241Am would give out roughly 33,000 x 5.486 = 181038 MeV of energy per second.So, now we know that that if you ingested one smoke detectors worth of 241Am dust, your newly contaminated bones would be receiving 

181038000000 * 1.60218e-19 =2.9005484097447e-8J

Of energy per second. The average person has roughly 2.5 kg of bone in their body, and for simplicity’s sake we’ll discount the bone marrow and flesh around the bone, as the impact on those is hard to calculate and probably not that significant. (as alpha particles don’t penetrate too far far anyway). To calculate the received dose, we divide 2.9005484097447e-8 by 2.5: 1.16021936e-8 Gy, Per second! From this point on, pretty much everything has to be a rough estimate, unfortunately, but for alpha particles, 1 Gy is approximately 20 Sv. So after imbibing 1 smoke detector you’re receiving 2.32043872e-7 Sv, which is admittedly miniscule, but this is each second. After one hour, you’ll have received 83.53579 Microsieverts - background radiation is only 0.17-0.39 Microsieverts an hour. Remember, 241Am deposits on your bones for decades; and this stuff has a half life hundreds of years long, so the same property that makes it last forever in smoke detectors will ensure it keeps irradiating you the entire time. Irradiated cells do not repair themselves, so damage will accumulate - and in just one day, you’ll have received 2.05 Millisieverts - in about six months, 50, enough to alter your blood chemistry. In 10 years, you’ll be consistently facing internal bleeding, but if you’re lucky, you’ll have it all out of your system before it would kill you, at around the fifty year mark.

But that’s one Smoke detector’s worth

Buy, disassemble, grind up and eat five of them, you’ll be dead in a decade. Manage fifty, and the next new year's will be your last. If you could source and stomach 1800, you’ll be gone before the month is up! And if somehow, you get your hands on 7,200 smoke alarms, congratulations! You get a week of unbelievable agony before passing away, anything but peacefully. So now you know! 

Works Cited

“Americium | Public Health Statement | ATSDR.” gov.cdc.wwwn, https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=809&toxid=158. Accessed 11 October 2022.

“Backgrounder On Smoke Detectors | NRC.gov.” Nuclear Regulatory Commission, https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/smoke-detectors.html. Accessed 7 October 2022.

“Basic Information on Radiation Units.” 2.3 Units of Radiation, 31 March 2019, https://www.env.go.jp/en/chemi/rhm/basic-info/1st/pdf/basic-1st-02-03.pdf. Accessed 16 October 2022.

“The Facts About Smoke Detector Radiation from Americium 241.” First Alert, https://support.firstalert.com/s/article/The-Facts-About-Smoke-Detector-Radiation. Accessed 7 October 2022.

Falck, Suzanne, and William Morrison. “Radiation sickness: Sources, effects, and protection.” Medical News Today, https://www.medicalnewstoday.com/articles/219615. Accessed 16 October 2022.

Nomiyama, Chizu, and John Chalmers. “Factbox: How much radiation is dangerous?” Reuters, 27 June 2019, https://www.reuters.com/article/us-japan-quake-radiation-idUSTRE72Q0HN20110327. Accessed 16 October 2022.

“Nuclear Decay and Conservation Laws | Physics |.” Course Hero, https://courses.lumenlearning.com/suny-physics/chapter/31-4-nuclear-decay-and-conservation-laws/. Accessed 16 October 2022.

“Smoke Detectors – Their Humble History.” SS Systems, 3 August 2017, https://sssystems.co.uk/latest-news/smoke-detectors-humble-history/. Accessed 27 September 2022.