Smoke Alarms and radiation from them

[Happy Days2021]

Why are smoke detectors with Americium exempt from leak testing when there are ones in older houses maybe 30 years old and one needs to open them up to change the battery. Surely the Americium could leak out over time from the ionisation chamber?

 

[sophiecentaur]

"surely"??
The Americium wouldn't be in the form of a powder. Afaik, most sources are encapsulated in matrix of glass or ceramic which would stay intact for thousands of years if it were not roasted or dissolved income strong acid.

 

[anorlunda]

Summary:: Smoke Alarms and radiation from them

Why are smoke detectors with Americium exempt from leak testing when there are ones in older houses maybe 30 years old and one needs to open them up to change the battery. Surely the Americium could leak out over time from the ionisation chamber?

It is not in the form of a gas or a powder.

https://hps.org/publicinformation/ate/q7445.html
Please be aware that there is a very small amount of 241Am, ~33.3 kBq in a smoke detector. This form of 241Am is embedded (fused) onto a layer of foil and does not pose any danger to you or your family; it cannot be wiped off, nor can it leach off. This is one of the reasons NRC originally authorized its use in the 1970s.

 

[Happy Days2021]

Why then do smoke detectors need leaked tested in schools as radiation sources and also solid sealed sources need leak tested in labs?

 

[berkeman]

Why then do smoke detectors need leaked tested in schools as radiation sources and also solid sealed sources need leak tested in labs?

Wasn't this already covered in your previous thread?

https://www.physicsforums.com/threads/radiation-leak-test-instruments.1002498/

 

[sophiecentaur]

Wasn't this already covered in your previous thread?

https://www.physicsforums.com/threads/radiation-leak-test-instruments.1002498/

Keep asking the same question until you get the answer you want, perhaps.

 

[Happy Days2021]

No I don't think my previous thread addressed how or why they could leak?

 

[berkeman]

No I don't think my previous thread addressed how or why they could leak?

We may end up merging your two threads. The Mentors are discussing it now...

 

[russ_watters]

Why then do smoke detectors need leaked tested in schools as radiation sources and also solid sealed sources need leak tested in labs?

Do you have a source for this requirement? I'm not familiar with it.

 

[Happy Days2021]

Yes, in England all schools must leak test sealed sources including smoke detectors used in Physics experiments

 

[russ_watters]

Yes, in England all schools must leak test sealed sources including smoke detectors used in Physics experiments

No, a source. A link to a description of the requirement.

...also, if you already know the test protocol I don't understand why you would be asking about test instruments in the other thread.

 

[Happy Days2021]

I know they need tested, but I don't know the how you actually do it part

 

[russ_watters]

I know they need tested, but I don't know the how you actually do it part

Well, since you said the UK I was able to find this (but you should really be doing your own homework here):
http://science.cleapss.org.uk/Resou...active-Substances-in-Schools-and-Colleges.pdf

I don't have time right now to dive into it, but the testing requirement and protocol are in there. But as a starting point, since this is the source of your concern it should be what frames your investigation.

 

[davenn]

Yes, in England all schools must leak test sealed sources including smoke detectors used in Physics experiments

Well, since you said the UK I was able to find this (but you should really be doing your own homework here):
http://science.cleapss.org.uk/Resou...active-Substances-in-Schools-and-Colleges.pdf

excellent info, but I didnt seen any mention of smoke detectors in there

reading through this thread, I continue to wonder if the OP has some misunderstanding on what is being referred to.
@Happy Days2021 you still haven't given an information source relating specifically to testing smoke detectors.
And since radioactive source smoke detectors have been made obsolete in most 1st world countries, I still can't help but wonder
why you are so fixated with them ??

Dave

 

[russ_watters]

excellent info, but I didnt seen any mention of smoke detectors in there

Page 32, but more broadly the entire document is about radiation sources used in school labs. If there were an unspecified one, the requirements would still apply.

And since smoke detectors have been made obsolete in most 1st world countries...

What?!

 

[davenn]

Page 32, but more broadly the entire document is about radiation sources used in school labs. If there were an unspecified one, the requirements would still apply.

Thanks for finding the bit about smoke detectors on page 31, I missed that

What?!

yup, here and in NZ at least ... the fire service will actively replace all radioactive source smoke detectors with the newer type
They called around home around 8 months ago and replaced our two, free of charge, and disposed of the radioactive source ones
in a safe manner.
Sorry of you Americans are behind the times

Dave

 

[russ_watters]

yup, here and in NZ at least ... the fire service will actively replace all radioactive source smoke detectors with the newer type
They called around home around 8 months ago and replaced our two, free of charge, and disposed of the radioactive source ones
in a safe manner.
Sorry of you Americans are behind the times

Ok, you're talking about the radioactive type, not smoke detectors in general. That's not what you said.

 

[davenn]

Awesome list
have several of them ( as ticked) always looking for more sources for the collection
Most of my sources are radioactive rocks, currently have ~ 15 samples with various mineral compositions

Cruising the old "op shops" ( second hand and antique shops) with my Geiger counter, which I need to do again,
been a while, brings up watches, clocks, occasional cup or plate.
The "hottest " natural source I used to be able to get to see what a thumb sized hunk of pitchblende
in the geology dept. where I did my studies. Even through the 1" think lead crucible it was still detectable

my 2 current detectors are these ...

one of these ( from China) ...

and 2 of these (from the Ukraine - sold like hotcakes during the Chernobyl chaos)

cheers
Dave

 

[davenn]

Ok, you're talking about the radioactive type, not smoke detectors in general. That's not what you said.

I said radioactive type

edit, ohhh maybe you were referring to post #14 ... I will edit

 

[berkeman]

They called around home around 8 months ago and replaced our two, free of charge, and disposed of the radioactive source ones
in a safe manner.

I read somewhere that they actually donated them to school science labs...

Spoiler

Well, to schools in other countries of course...

 

[russ_watters]

The standard for UK schools it says this:

The residual risk is low with the control measures in place.
Note: these control measures are not required for smoke alarms when used in the home, as
they are extremely unlikely to suffer damage in the normal position, fixed to the ceiling.

So they are basically saying that they don't leak in normal use, but you never know what might happen if you let school kids abuse them.

 

[Vanadium 50]

but you never know what might happen if you let school kids abuse them.

I'm imagining the old American Tourister ads.

And since smoke detectors have been made obsolete in most 1st world countries

What?!

You didn't hear? Building fires have been banned.

And since radioactive source smoke detectors have been made obsolete in most 1st world countries

The US is, last I checked, the 1st world. You can even get Vegemite if you know where to look. Not sure why anyone would want to.

According to Home Depot, ionization (they never say "radioactive source") detectors are the most popular. I'm not surprised. They are safe, inexpensive and effective.

They used to be uniformly superior to photocell detectors. Photocells are getting better, thanks to two developments: cheap computation, and blue LEDs. Photodetectors were less accurate - less sensitive at the same threshold, or if you lowered the threshold, more prone to false alarms. Shorter wavelengths help, comparing responses at different wavelengths helps, looking at the time profile helps, and tiny little DSP chips put it all together. And while in principle CO detection is independent of smoke sensor type, if you already are going to put some intelligence on your smoke detector, you can combine the information from the smoke detection with CO and do a better job on both fronts.

 

[davenn]

Vegemite if you know where to look. Not sure why anyone would want to.

It's very yummy

 

[sophiecentaur]

It's very yummy

Nothing like as nice as the sharper taste of Marmite. I feel sorry for Aussies, in that respect. They seem to think that the poor relative is as good.

 

[meb68]

Thanks for finding the bit about smoke detectors on page 31, I missed that
yup, here and in NZ at least ... the fire service will actively replace all radioactive source smoke detectors with the newer type
They called around home around 8 months ago and replaced our two, free of charge, and disposed of the radioactive source ones
in a safe manner.
Sorry of you Americans are behind the times

Dave

We're "behind the times" when it comes to guns too, dave.

Anyway, it's unbelievable to me that such a dangerous radioactive alpha-particle-emitting material (americium) was ever approved for use in these things which are in tens of millions of homes in this country.

 

[russ_watters]

Anyway, it's unbelievable to me that such a dangerous radioactive alpha-particle-emitting material (americium) was ever approved for use in these things which are in tens of millions of homes in this country.

It's about understanding and properly mitigating risk. It just isn't that high even if described in scary sounding terms.

 

[Vanadium 50]

Typical radiation doses from smoke detectors is the same as eating 0,1-0.5 bananas per year.

An interesting question would be if the Amerecium is the most radioactive part of the smoke detector, or which has more radiation at a distance of, say 1 meter: ionization or photodetection. The answer is not obvious.

 

[Vanadium 50]

I ws originally thinking about glass and potassium-40. But...

Now that I think of it, ionization-type may actually reduce radiation exposure. By ionizing dust, it will collect on surfaces rather than stay in the air (kind of the point). Mineral dust contains radioisotopes - uranium, thorium and polonium. In principle, an ionization smoke detector will reduce exposure to some natural radioactivity.

In practice, this effect is surely too small to detect. But my point is that it's not immediately obvious even in which direction the sign is.

 

[sophiecentaur]

Are we getting this into a proper perspective? The possible risk of death in a house fire is what needs to be compared with very low risks of radiation damage from the 'offending' detectors.
I read a few web documents which were of varying degrees of quality but the opinion seems to be that a functioning smoke detector in a home is likely tohttps://www.health.ny.gov/prevention/injury_prevention/children/toolkits/fire/smoke_alarms_effective_preventing_deaths.htm. The actual statistics is obviously complicated but that link suggests that 890 deaths would be avoided (in US?) per year if everyone had a functioning detector. How many deaths, on the other hand, have been caused by damaged detectors due to escape of radioactive materials? This link suggests the exposure is less than the background radiation levels.
Thing is, radiation, like flying, has a very high perceived risk and we tend to overestimate the dangers associated with both.

PS the number of deaths due to using wood fires in cooking in developing countries is pretty vast. This link has evidence that 3.8M deaths are caused through the use of wood fires in cooking. Scary but not a simple problem to solve in developing countries. (Barbecues?!)

 

[davenn]

Anyway, it's unbelievable to me that such a dangerous radioactive alpha-particle-emitting material (americium) was ever approved for use in these things which are in tens of millions of homes in this country.

You are really not understanding how low the risk is. They are incredibly low level sources
The ones I have played with, with a Geiger counter, were not even detectable from 1m away.

Alpha particles do not travel very far ... they are a Helium nucleus and will pic up a couple of free electrons very quickly and become neutral