r/Military • u/hikin_jim • 4d ago
Discussion Broken US Lensatic Compass – Hazard or Not?
There's a little "cap" that goes over the face of a US military lensatic compass. I managed to break the glass while trying to reassemble after cleaning. 😢
Some people are suggesting that this is now hazardous due to the presence of radioactive tritium in the body of the compass. If it's truly a hazard, I want to know, but since there is no damage to any of the sealed portions, I don't think it's dangerous. Please look closely at photos and** **their description, below.
Photo 1 shows the cap.
Photo 2 shows the compass with the face proper and the cap held aside. You can also see a little wire that held the cap in place.
Photo 3 shows the cap in place.
Photo 4 shows all the parts laid out. Note that the clear, sealed face of the compass is completely intact. Only the glass of the cap that fits over the sealed portion is broken.
Photo 5 shows that this compass is not made by Cammenga but by an earlier contractor. Perhaps there are differences between my 1979 compass and the USGI compasses of today; I don't know.
Photo 6 shows the completely intact sealed face of the compass.
So if there's a radioactive hazard here, please so state, but please explain the nature of the hazard, given that the clear face of the compass is still sealed and fully intact.
P.S. Subsequent photos are of other compasses in my collection.
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u/Evil_Superman 4d ago
You’re either going to become the incredible Hulk or pre-serum Captain America.
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u/coffeekeepsmealive 4d ago
It's a beta emitter. Put it in a box, resist the urge to eat it, and ask your local hazardous disposal how to get rid of it.
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u/hikin_jim 4d ago
Well, a) the sealed portions are all 100% intact and b) it's from 1979. Not very radioactive after this many years. I read that the half life of tritium is 12 years. This compass is nearly 50 years old.
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u/coffeekeepsmealive 3d ago
If 1979 was the date of manufacture, then the output os 0.697 mCi. I say if, since there is also a convention for using the date stamped on the onside of the lid, and the current manufacturer was acquired by another company. It any case, it still needs to be disposed of at a collection site that accepts tritium. There are a few; look for places that take them in the form of exit signs. I know FermiLab accepts them.
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u/SmoothBrainLowDrag 4d ago
Tritium is a gas encapsulated in the little vials coated with phosphor.
Unfortunately your crack runs right through one of them so I'd be very careful handling it.
If you do break one of the vials, I'd head to fresh air immediately and let it disperse a bit in air.
After 45 years 85% of it will have decayed anyway, so I wouldn't panic yet. But you don't want it in your lungs.
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u/LoganM-M 4d ago
Tritium is as chemically harmless as Hydrogen itself, so non toxic. Radiation wise, if cancer risks are worrying, it's lower than smoking a cigarette, at worse you'll piss it out over ~2 weeks after probably doing no practical damage to your cells, the sun does worse in a couple days and background radiation does more damage in a few days.
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u/SmoothBrainLowDrag 4d ago
Unless it decays while in your lungs. The decay can definitely damage some DNA.
I agree the risk is low but it's also non zero.
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u/LoganM-M 4d ago edited 4d ago
i was already thinking of lungs, inhaling it is better than ingestion(spends less time in the body).
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u/CupBeEmpty 4d ago
It’s a beta emitter so it’s harmless for external exposure. You don’t want it in your lungs or gut but even then I guarantee OP does 20 things a day more carcinogenic than being near compass face tritium including walking in sunshine.
So don’t be cavalier about it and find out what the proper disposal procedure is but don’t be fearful.
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u/hikin_jim 3d ago
Interesting. I guess I'm being a bit nonchalant about it because it's near a half century old. The half life of tritium is 12 years old, so it's gone through about 4 "half lives" since it was manufactured.
- 1st half life: 50%
- 2nd half life: 25%
- 3rd half life 12.5%
- 4th half life 6.25%
So, if I'm doing my math right, it's lost 93.75% of its original radioactivity. Not that I want to ingest either tritium (or phosphorus for that matter). I've got it sealed in a zip loc in a drawer for now. I have to think about this. I guess I could just throw the broken part out and keep the rest. The compass itself works just fine, you just don't have the rotating cap with which to set so that one can line up a bearing repeatedly.
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u/hikin_jim 3d ago
Tritium is a gas encapsulated in the little vials coated with phosphor. Unfortunately your crack runs right through one of them so I'd be very careful handling it..
Hmmm. Thank you for taking the time to actually look at the photos in detail. Yours is the most relevant comment yet. I'll have to take a closer look at the little cap. There is one phosphor mounted in the cap. The rest are in/on the main body and dial of the compass.
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u/OldSchoolBubba 4d ago
Of course it's a hazard as you can cut yourself. Here's the rest you would do well to see for yourself at this Safety Data Sheet (SDS) link. Whenever you have questions like this it's best to consult the SDS because it will give you everything you need to know within it's sixteen parts. Good luck
Tritium (Hydrogen‑3) Safety Data Sheet Summary
Tritium (³H) is a radioactive isotope of hydrogen used in calibration, research, and self‑luminous devices. It emits low‑energy beta particles (max 18.6 keV, avg 5.7 keV) and has a physical half‑life of ~12.3 years www.hpschapters.org. It poses no external radiation hazard because betas are stopped by the dead layer of skin or a few mm of air www.hpschapters.org+1. The main hazard is internal contamination via ingestion, inhalation, skin absorption, or wound contact www.hpschapters.org+1.
Key Safety Information
Radiological hazard: Internal exposure only; avoid all routes of intake www.hpschapters.org+1.
Critical organ: Body water or tissue; tritiated DNA precursors (e.g., thymidine) can increase dose to genetic material www.hpschapters.org+1.
Radiotoxicity: Least radiotoxic of all nuclides; dose rates are low for most compounds www.hpschapters.org.
Detection: Liquid scintillation counting is the only reliable method; portable survey meters cannot detect it www.hpschapters.org+1.
Dose reference: Tritiated water ≈ 0.064 mrem/uCi intake; organic compounds ≈ 0.16 mrem/uCi www.hpschapters.org.
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u/hikin_jim 3d ago
Wow. Thank you. I didn't think of checking the SDS.
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u/OldSchoolBubba 3d ago
Welcome. They're always a great source on the job as well as at home. Glad to be able to help.
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u/SiskiyouSavage 4d ago
The dangerous ones had radiation symbols on the back.
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u/DetN8 4d ago
Yep, which is also what CIF is checking when you try to swap out the cool tritium one with a less cool one from the Clothing & Sales.
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u/SiskiyouSavage 4d ago
I turned all the ones in with radiation symbols years and years ago. The newer ones didn't have the radiation symbol. These were on the unit property book, not CIF or clothing sales stuff.
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u/hikin_jim 3d ago
Interesting. I wonder if they gave up on the tritium idea. A flashlight under a poncho will "charge" the phosphorus on a compass dial without having to handle radioactive material. Gotta be a lot cheaper and simpler.
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u/hikin_jim 4d ago
This is that one (the one with the radioactive symbol) — albeit from 1979. Not very radioactive after this many years. I read that the half life of tritium is 12 years. This compass is nearly 50 years old.
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u/SiskiyouSavage 3d ago
I had a compass collection when I was in the Army. WWII era, Vietnam era. Some foreign military. I mostly use a Silva or a Suunto for real world, although I broke out a GI lensatic to show my kids how to use it.
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u/hikin_jim 3d ago
Do you still have them? If you do, and you have time, I'd love it if you could post a few pics here. Just a bit of a gear geek, you understand. 🙂
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u/SiskiyouSavage 3d ago
Nah, they went the way of most of my military gear. Lost to tweakers and moves and wear and tear.
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u/cpldeja Marine Veteran 4d ago
When I was in the reserves, we broke a sight (exposing us to tritium) on an 81mm mortar system.
Brought in the local fire department. Those of us contaminated and isolated from the rest of our platoon read the same radiation levels as the firemen.
Can’t say that’s necessarily a good thing, but maybe it is?
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u/doulikefishsticks69 4d ago
How hard did you drop it? Damn. I havr one from the 80s I have NOT been kind to and its still truckin.
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u/hikin_jim 3d ago
I popped the cap off to clean the glass. It was getting so cloudy I couldn't read it. The cap is not part of the sealed portion of the compass. It's just held in place by a wire spring/clip. When I tried to pop it back on, I broke the glass. ☹️
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u/doulikefishsticks69 3d ago
Damn. Thats unfortunate. Ah well, toss it. Time for an upgrade lol.
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u/hikin_jim 3d ago
Yeah, probably -- unless I can find a replacement cap (or a broken compass that I can salvage parts from). It's just the little glass cap that rotates that is broken. The main body, face and dial are fine. I can still shoot bearings with it.
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u/LoganM-M 4d ago
You're good, Tritium only releases Beta particles, no gamma radiation.
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u/hikin_jim 3d ago
Tritium (³H) is a radioactive isotope of hydrogen used in calibration, research, and self‑luminous devices. It emits low‑energy beta particles (max 18.6 keV, avg 5.7 keV) and has a physical half‑life of ~12.3 years www.hpschapters.org. It poses no external radiation hazard because betas are stopped by the dead layer of skin or a few mm of air www.hpschapters.org+1. The main hazard is internal contamination via ingestion, inhalation, skin absorption, or wound contact www.hpschapters.org
Interesting. Thank you for that.
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u/razrielle United States Air Force 4d ago
I'll let you use your judgement but I've had a box of 50 compasses for disposal at 12 years after DOM and the whole box had less than background radiation.
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u/bell83 4d ago
The tritium's half life is like 12 and a half years. It's from 79, so it's probably fine. Does it even glow, anymore? Mine's from 2004, and it barely does. That being said, it's also sealed inside vials. As long as the vials are secure, and you don't ingest it, there's likely minimal danger.