Touched a smoke detector and then put hands in mouth?

[vvcurious]

Hi.

I have a very embarrassing question to ask.

I was changed the battery in my smoke detector, which is the sort that uses americium to work. I have a bad habit of chewing and swallowing my nails, and also picking and my nose and swallowing the stuff from my nose, too.

I'm paranoid that I inadvertently did one of those two (or both?) after handling the smoke detector.

I recently learned that the americium seems to just be painted on to a metal button inside the plastic casing, which isn't even really well contained in terms of my own smoke detector. I always thought they were super enclosed in a very non-destructable metal casing. SO, basically, now I'm paranoid I ingested some of the americium by these series of actions.

Is that even a rational thing to worry about? Am I missing some details about how smoke detectors work? I understand they are alpha emitters, but since the question is whether or not I ingested it, and not whether or not I got in on my skin I guess it could be.

I came across this lab manual that says you should wash your hands when handling radioactive substances, even after touching a smoke detector, so now I'm like "Ahhh!".

http://myslu.stlawu.edu/~jmil/physics/labs/152_lab/inactive/smoke_detector_old.pdf

 

[Bandersnatch]

Nothing to worry about. It's an extremely weak radiation source in the form that is not readily absorbed by body tissues.

Here's some safety info from the US Nuclear Regulatory Commission:
https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/smoke-detectors.html

The study also looked at doses from misuse. It found that a teacher who removed the source from a smoke detector could receive a dose of 0.009 millirems per year from storing it in the classroom. The teacher would get another 0.001 mrem from handling it for 10 hours each year for classroom demonstrations, and 600 mrem it he or she were to swallow it.

For comparison, 600 mrem is about half of what you'd get from a full-body CT scan.

Here's info from Australian Radiation Protection and Nuclear Safety Agency:
https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/smoke-detectors

(...)the hands are very much less sensitive to radiation than internal organs and the time of exposure is likely to be only a few minutes per year, no significant radiation exposure would occur.

The radioactive source in a smoke alarm is extremely insoluble and, if swallowed, would not be absorbed into the body but would pass through the digestive system.

And an answer to a similar question from the Health Physics Society website:
https://hps.org/publicinformation/ate/q11701.html

It is impossible for the 241Am to leach out over time while in your home. Not even small particles of it will flake off. The americium is electroplated onto the metal disk, just like chrome is plated on a car bumper or door handle. It could be removed only by grinding or by using very strong chemical acids. Additionally, the americium is protected by a thin, gold-metal layer that is very chemical resistant. So, the 241Am on the disk of a smoke detector can be removed only if it is done intentionally and by using very aggressive methods.

(I'd treat the safety warning from the linked document as the teacher hammering general good practices into students' heads)