Radiation Safety: Understanding Exposure and Risk

[spark90]

Recently when cleaning, I opened the cover of our ionisation smoke detector and as I was touching all around the inside of the smoke detector with my bare hands and most importantly including all the sides of the ionization chamber with the radiation symbol on it which contains the radiation, for around 5-6 minutes, have I:-

1. Increased my risk of taking cancer now or in future from touching the outside of the ionization chamber with the radiation-would there have been a lot of exposure?
2. By touching the ionization chamber (which is black on the outside-perhaps hard plastic) could I have loosened it in any way allowing the radiation to be exposed and to escape into the house? This is a big concern for me.
3. Can the radiation easily become loose or fall out of the ionisation chamber?
4. Would dust on my hands afterwards just have been household dust or was it from the radiation? More to the point does the decay of americium-241 produce dust
5. As there are slats on the side of the ionisation chamber, could dust from the americium escape here?

This panicked me when I realized I had been touching the actual ionisation chamber and I wanted some information on the safety.

 

[russ_watters]

Recently when cleaning, I opened the cover of our ionisation smoke detector and as I was touching all around the inside of the smoke detector with my bare hands and most importantly including all the sides of the ionization chamber with the radiation symbol...

Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.

1. Increased my risk of taking cancer now or in future from touching the outside of the ionization chamber with the radiation-would there have been a lot of exposure?

No.

2. By touching the ionization chamber (which is black on the outside-perhaps hard plastic) could I have loosened it in any way allowing the radiation to be exposed and to escape into the house? This is a big concern for me.

3. Can the radiation easily become loose or fall out of the ionisation chamber?

4. Would dust on my hands afterwards just have been household dust or was it from the radiation? More to the point does the decay of americium-241 produce dust.

5. As there are slats on the side of the ionisation chamber, could dust from the americium escape here?

That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.

 

[sophiecentaur]

Americium is the source that's chosen as it's a good source of Alpha Particles (doubly ionised Helium Nuclei). These are massive great particles and, once they have slowed down in the detector, they become harmless Helium Atoms. No Beta Particles or gamma photons.
I think that. nowadays, anything that's radioactive and for use by the public will have passed a lot of risk assessments. I guess that eating the source could be a finite risk but the Alpha source can only damage tissue that out actually come into contact with. I guess the cell would pass straight through.

I would say that the risk of any possible radiation injury is totally insignificant, compared with the reduction of risk of injury or death in a fire.

 

[anorlunda]

If you read the labels carefully, you should see, "Do not ingest." I assume you didn't eat it, correct? Then you should be OK.

 

[spark90]

If you read the labels carefully, you should see, "Do not ingest." I assume you didn't eat it, correct? Then you should be OK.

No, I was just concerned that the dust into my eyes and hence was inhaled when I opened the smoke detector cover was dust from the decay of the americium inside the smoke detector.

 

[spark90]

Americium is the source that's chosen as it's a good source of Alpha Particles (doubly ionised Helium Nuclei). These are massive great particles and, once they have slowed down in the detector, they become harmless Helium Atoms. No Beta Particles or gamma photons.
I think that. nowadays, anything that's radioactive and for use by the public will have passed a lot of risk assessments. I guess that eating the source could be a finite risk but the Alpha source can only damage tissue that out actually come into contact with. I guess the cell would pass straight through.

I would say that the risk of any possible radiation injury is totally insignificant, compared with the reduction of risk of injury or death in a fire.

Thank you for your reply. As my smoke detector is 27 years old I was worried health and safety wasn't as good then. As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust and could this have been the dust i encountered as it states online inhalation of this dust collects in lungs.

 

[spark90]

Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.

No.

That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.

Thank you for your reply. As my smoke detector is 27 years old I was worried health and safety wasn't as good then. As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust and could this have been the dust I encountered as it states online inhalation of this dust collects in lungs.
Also can dust/alpha escape the slats at the sides of the ionisation chamber?
Here is what my detector looks like attached.

 

[anorlunda]

I would expect zero dust. The Americium is encapsulated in a coating.

In the days of the Manhattan Project, plutonium was extra dangerous because of spontaneous sintering that shed dust, contaminating the room and everything in the room. But soon after WWII, the bomb makers learned that a simple coating eliminated that specific problem.

Here's a declassified picture from a hydrogen bomb factory.

 

[russ_watters]

As my smoke detector is 27 years old I was worried health and safety wasn't as good then.

Well that's a concern; please check it, because it may have a 10-year lifespan. That's a significant safety risk if it is expired.

As dust from the inside of the cover could have been inhaled when falling into my eyes, are you aware of whether when americium decays over the years does it produce dust...

It does not.

Also can dust/alpha escape the slats at the sides of the ionisation chamber?

It's not dust. Yes, at least some of the alpha particles escape.

 

[sophiecentaur]

That's a significant safety risk if it is expired.

OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ.

 

[spark90]

OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ.

Not sure what you mean by that. I have anxiety and sm just looking reassurance, what do you mean risk of nuclear radiation?

 

[Keith_McClary]

Most smoke detectors use americium-241 as their source. Some early models used radium-226, and commercial smoke detectors and some residential units used nickel-63. The types of radiation from these sources cannot make anything else radioactive.

• Ni-63 emits beta particles, which can travel a few feet but cannot penetrate a smoke detectors plastic housing.
• Am-241 and Ra-226 primarily emit alpha particles. These particles only travel a few inches, are easily stopped and only present a health hazard if taken into the body.
• Am-241 and Ra-226 also emit gamma radiation in an amount so low it cannot be distinguished from natural radiation from space and the earth.

The radioactive sources are in a form that does not break down or corrode over time. The source is sandwiched between two layers of metal and rolled thin. This "foil" is sealed inside the ionization chamber. The seal can only be broken by the deliberate use of force, such as taking a hammer to the smoke detector. The NRC discourages this kind of intentional destruction. In a fire, the sources would release less than 0.1 percent of their radioactivity.
US NRC

Smoke detector internals.

 

[sophiecentaur]

Not sure what you mean by that. I have anxiety and sm just looking reassurance, what do you mean risk of nuclear radiation?

Sorry if I upset you but you have already been given plenty of reassurance with good information about the actual risk of radioactive exposure. But using the same smoke detector for all that time could be regarded as foolhardy. It's all a matter of getting risks in proportion and the risk of an undetected fire is something that can be taken care of easily by a trip to the DIY shop. If you are concerned by radiation risks then buy a type of smoke detector that doesn't use a radioactive source.
Afaics, the most important thing for you is to get a new detector PDQ (and you could check on your CO detector if you have one - the lifetime of those is very limited)

 

[spark90]

Do you have a make and model or pictures of this smoke detector? Because mine are not designed to be opened, and I see no obvious way to even do it without breaking it.

No.

That's...not what "radiation" is. In this case, it's a free helium atom nucleus, not a dust. There isn't enough Americium in a smoke detector to be harmful in any way, and in any case the radiation (alpha particles) can't penetrate your skin.

In regards to you said "thats not what radiation is", I am just interested what you mean by that, thanks

 

[russ_watters]

In regards to you said "thats not what radiation is", I am just interested what you mean by that, thanks

Well you keep asking if it's dust and also don't seem to be distinguishing between radiation and radioactive material.

 

[spark90]

Well you keep asking if it's dust and also don't seem to be distinguishing between radiation and radioactive material.

I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.

 

[russ_watters]

I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.

I know - that was just an answer to your question.

 

[spark90]

I know - that was just an answer to your question.

Thank you really appreciate your time, still don't understand really if americium breaks down to produce dust which can escape the ionisation slats-could you briefly explain that...and I promise that is my last question. You are very kind taking the time to reply.

 

[jbriggs444]

I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.

When a radioactive decay occurs (in this case an alpha decay), the parent atom emits the daughter particle and, as a result, becomes a different type of atom. One can look up Americium 241 on wikipedia and find that the alpha decay results in Neptunium 237.

The alpha particle is essentially a Helium nucleus. Two protons and two neutrons. No electrons, so it has a charge of +2 from the protons. The "radiation" is the alpha particle.

The loss of two protons and two neutrons means that the result (Neptunium) has an atomic number that is two less than that of Americium. If you look at the periodic table you'll find Americium and Neptunium on the bottom row with Neptunium at atomic number 93, two slots to the left of Americium with atomic number 95 just as one would expect.

Now I am just a school boy physics geek and know not too much about the engineering or chemistry of this stuff, but I'd expect that the result of the decay of the Americium dioxide within a pellet to result quickly in a molecule of Neptunium dioxide still within the same pellet. One would expect the designers to have arranged for the decay not to result in decay products falling clear of the original matrix.

But in any case, the Neptunium 237 is much less radioactive than Americium 241. By a factor of half a million to one. (Based on a comparison of half-lives).

 

[spark90]

When a radioactive decay occurs (in this case an alpha decay), the parent atom emits the daughter particle and, as a result, becomes a different type of atom. One can look up Americium 241 on wikipedia and find that the alpha decay results in Neptunium 237.

The alpha particle is essentially a Helium nucleus. Two protons and two neutrons. No electrons, so it has a charge of +2 from the protons. The "radiation" is the alpha particle.

The loss of two protons and two neutrons means that the result (Neptunium) has an atomic number that is two less than that of Americium. If you look at the periodic table you'll find Americium and Neptunium on the bottom row with Neptunium at atomic number 93, two slots to the left of Americium with atomic number 95 just as one would expect.

Now I am just a school boy physics geek and know not too much about the engineering or chemistry of this stuff, but I'd expect that the result of the decay of the Americium dioxide within a pellet to result quickly in a molecule of Neptunium dioxide still within the same pellet. One would expect the designers to have arranged for the decay not to result in decay products falling clear of the original matrix.

But in any case, the Neptunium 237 is much less radioactive than Americium 241. By a factor of half a million to one. (Based on a comparison of half-lives).

Thanks for your time, I was really just wanting to know a simple answer to whether americium decays over the years producing dust which can escape the ionisation chamber. Thanks again

 

[gmax137]

I was really just wanting to know a simple answer to whether americium decays over the years producing dust which can escape the ionisation chamber

No.

 

[sophiecentaur]

I was really just wanting to know a simple answer to whether americium decays over the years producing dust

The Americium is embedded in a block of plastic. No atoms of anything leave that block of plastic - except for high speed Helium nuclei. They will travel just far enough to operate the detector (perhaps 1mm) and then they are stopped. They can no longer be regarded as Radioactive products but will find their way out into the atmosphere or get embedded in the case of the detector. The case cannot become 'radioactive' when that happens.
I can't help thinking you are finding it a bit of a disappointment that the situation is not slightly risky. The only way you could get damaged by the Americium could be if you shredded / crushed the source and then embedded it into your brain, lungs or gut. I have already made the point that the risk of injury or death through an undetected fire is seriously significant. You need to get your priorities in proper balance. One small slip in your (I hope) scrupulous behaviour regarding Covid-19 puts you in far more danger than anything from that smoke detector.

 

[Vanadium 50]

You need to get your priorities in proper balance. One small slip in your (I hope) scrupulous behaviour regarding Covid-19 puts you in far more danger than anything from that smoke detector.

Well, since you urged being quantitative, I don't think this is true for most people. Under 50 years old, your odds of dying of Covid are 10x the odds of dying in fire. I don't know what "far more danger" means - a factor of 2? That would mean "one small slip" needs to increase your risk by at least 20% or so. That doesn't sound like a "small slip".

So, while I think this isn't the best example, I agree with the sentiment that risks need to be quantified, and that the risk of an alpha source (unless you break it apart and eat it, or something equally insane) is less than the risk of fire.

 

[Keith_McClary]

type of smoke detector that doesn't use a radioactive source.

https://www.nfpa.org/Public-Educati...ment/Smoke-alarms/Ionization-vs-photoelectric

 

[Lorenzo Diego]

I am just a member of the public and know nothing about radiation. I just assumed amercium decays over time and would produce dust which could escape the slats of the ionisation chamber. Sorry I have anxiety and looking for some facts.

Radiation is the energy emission of electromagnetic waves or subatomic particles. Therefore, heat, light, and electricity are examples of radiation. When you go to the beach to get a suntan, ultraviolet radiation from the sun hitting your skin causes that. When you feel your skin warming up, that is from infrared radiation from the sun. When you go to the dentist and get an x-ray performed, that is done from high-energy waves when penetrate your skin and muscle and expose the film on the other side.
Radiation comes in two flavors, ionizing and non-ionizing. Ionizing radiation is basically the type of radiation that turns something into ions. Atoms or molecules affected by ionization are turned into ions through the loss of electrons from high speed particulars "radiating" the substance. The radiation emitted from an atomic bomb is an example of ionizing radiation. The sun also produces ionizing radiation in the form of x-rays and gamma rays.
An example of non-ionizing radiation is the energy emitted from your microwave oven. The microwave oven converts electricity to electromagnetic waves (e.g., microwaves). These waves makes molecules (typically water in your food) to "bounce" around causing heat. In turn, any food that has sugars or fats will be heated from the heated water molecules.
Radioactive material, on the other hand, is material that has nuclides that degenerate spontaneously releasing radiation. A good example of this is radium which is found naturally in rocks such as uranium (itself being a radioactive material) and even granite. As the radium decays, it releases radon gas, which is why it is good to check for radon levels in your home that can seep from the bedrock underneath the foundation.
So, the next time you turn on a flashlight, the light you produced is radiation. The same is true for a candle you lit. And, the heat emanating from the candle is also radiation. And, when you walk in the countryside, pick up a rock. It might be radioactive material, though not dangerous (most likely).

 

[sophiecentaur]

Under 50 years

I wish!

your odds of dying of Covid are 10x the odds of dying in fire.

I was referring to the odds of injury due to the contents of the detector - but I could have made it clearer.

 

[N1206]

sophiecentaur said: "OMG. Risk of burning and nuclear radiation at the same time. Get A New One PDQ."

Sophiecentaur was making a serious joke.
No, your smoke detector is not a source of hazardous radiation.
But the manner in which it works is that the decaying radioactive element sends energy toward a receiver. The particulates in smoke block the energy from reaching the receiver, setting it off.

Now regulators make sure consumer products are built to the lowest common denominator, i.e. what's the STUPIDEST thing a consumer can do, and will that be lethal? So the detector has a very small quantity of radioactive material in it to work--but radioactive materials decay over time--half-lives. And they become less radioactive, by half, as they degrade, putting out half the energy they did the period before. The common 10 year life let's the detector do its work while never being a source of energy that could ever be hazardous.

At 27 years old, there is a very, very good chance your detector wouldn't actually go off in a fire: its source has gotten too weak to do its job, or the receiver isn't working right, or it didn't have the annoying warnings that modern ones have to warn you they are NFG.

You should replace that thing, pronto.
It may be giving you a false sense of security.
There's a high probability at 27 years old that it is NFG.

 

[jbriggs444]

So the detector has a very small quantity of radioactive material in it to work--but radioactive materials decay over time--half-lives. And they become less radioactive, by half, as they degrade, putting out half the energy they did the period before. The common 10 year life let's the detector do its work while never being a source of energy that could ever be hazardous.

At 27 years old, there is a very, very good chance your detector wouldn't actually go off in a fire: its source has gotten too weak to do its job, or the receiver isn't working right, or it didn't have the annoying warnings that modern ones have to warn you they are NFG.

The half life is unlikely to be the issue. For Americium 241 the half-life is 432 years. You may be right about the reliability of the receiver.

 

[Keith_McClary]

These ionization smoke alarms are alerting tens of minutes slower than the other type, photoelectric smoke alarms, in the deadly smoldering stage of a fire. They are also more prone to nuisance false alarms from ordinary cooking and steam from showers.

Photoelectric smoke alarms sound tens of minutes faster than ionization smoke alarms during smoldering stage fires with significantly fewer false alarms. Furthermore, their performance in flaming stage fires is comparable to ionization alarms, making the photoelectric alarm the best choice.

https://neofpa.org/smoke-alarms/half-smoke-alarms-fail/

 

[spark90]

Can I say a massive thanks to everyone for replying I really appreciate it. The reason I went on a bit was because I read on another site a post that concerned me:- "It is the alpha recoil reaction that can destroy the thin coating over the source and allow source material to recoil out of the source." Apparently this caused a yellow discharge from someone's ionisation chamber, although the activity was 5 microcuries. That was why I asked so many questions on here because I know so many of you were experts. Thanks again

 

[sophiecentaur]

because I read on another site a post that concerned me:

It would have been a good idea to have quoted that in your first post.

 

[spark90]

Yeah that is true. I just wasn't sure if it sounded daft or whether it was reasonable

 

[Keith_McClary]

caused a yellow discharge from someone's ionisation chamber

a typical modern detector contains about 1.0 microcurie of the radioactive element americium, which is equivalent to 37 kilobecquerel (37,000 decays per second), or 0.33 micrograms of americium oxide (AmO2).

This is the weight of one maize pollen grain. Even if all the Am was released, it is hard to see how a visible discharge would result.

 

[Phinrich]

Good day.

As a Radiation Protection Specialist, with 30 years of experience, I can assure you that the risk to you, from fiddling with the Americium-241 source inside your smoke detector, is negligible. The quantity of radioactivty in such a detector is, in regulatory jargon, Exempt from being regulated. This means that the radiation dose, which anyone can be exposed to, by fiddling with the source, is considered too small to cause any harm. Yes, this does come from very detailed risk assessments which have considered ALL potential scenarios of "playing with the source" and the resultant radiation dose. Wherever you are living, if it was considered that the smoke detector could be harmful it would never have been sold to you as a member of the general public. I hope this puts your mind at ease. Of course, there's no harm in washing your hands after touching the source which I am sure that you did. If you didn't the potential radiation dose would still be negligible.

Paul

 

[Phinrich]

Having said that, it's good practice to keep away from radiation if you can avoid it. That's easier said than done as radioactivity is a natural phenomenon and we are all surrounded by it every day without even being aware.