Old Army Smoke Grenade- is it safe to keep inside?
December 14, 2022 6:24 PM   Subscribe

In the "Intruders Detected" metatalk thread about random objects appearing in your home, I mentioned that the prior owners of our house left what I think is probably a Vietnam War era smoke grenade in the basement. The smoke grenade in question. It was pointed out to me that this might not be a safe thing to store in the house.

Does anyone know how stable these things are? We've had it sitting on a shelf in the basement for close to 20yrs without incident. Long term I will take it to the police for disposal, but for the moment I stuck it inside a small, empty safe on the theory that if it decides to spontaneously combust that will keep it from starting a fire. Any tips, anecdotes, advice or random speculation about how safe it is, what to do with it, etc. is welcome.
posted by Larry David Syndrome to Home & Garden (17 answers total) 1 user marked this as a favorite
I was wondering about that, and I appreciate this post and the opportunity to satisfy my curiosity.

The fact that it’s "red smoke" makes me think it’s main purpose is signaling rather than any kind of anti-personnel action, so less toxic than it might have been, perhaps.
posted by jamjam at 6:38 PM on December 14, 2022 [1 favorite]

But red inorganic compounds do include cinnabar (mercury sulfide), and I don’t know how the military felt about the toxicity of mercury back then.
posted by jamjam at 6:45 PM on December 14, 2022 [1 favorite]

"Long term I will take it to the police for disposal"

Even if it's completely "safe", who wants their basement filled up with red smoke if by chance the thing somehow gets ignited? Imagine having a fire in your basement and that thing goes off. What's the likelihood that any firefighters are going to want get anywhere near some unidentified red smoke?

Why not just take it to the police for disposal now? If it's something you're going to do anyway, and you have at least some level of concern about whether it's safe, then now's the time to get rid of it.
posted by jonathanhughes at 7:20 PM on December 14, 2022 [4 favorites]

I have no expertise in the field whatsoever, but if it was ever a functional incindiary device I would not keep it sitting around as a curiosity. At a minimum, it would be a hazard during a fire caused by something else.

I would call your local information service for guidance on disposal of potentially flammable waste. Taking it to a fire station is probably also a safe choice.

Please note: these are suggestions based on safety, not legality. I have no idea whether you could get in trouble for even having or for turning over such a device.
posted by sindark at 7:22 PM on December 14, 2022 [1 favorite]

Best answer: I'm the one who first commented on that, and I'll be honest that if it was mine, I'd give some thought to if there was somewhere in the middle of nowhere to try and set it off, thanks to my inner 12 year old. But really, the smart thing would be to gift it to the bomb squad, fire department, hazardous waste station, or wherever you can get to accept ti.

Like others have said, it's a risk if there is a fire, and it's a (very slight) risk of starting a fire or more likely, filling your house with smoke. (Which, potentially, could cause a lot of damage on its own.)

You aren't gaining anything by keeping it around, there is only added risk, however small. It should only take a few phone calls to find out where it can be taken.
posted by Dip Flash at 7:32 PM on December 14, 2022 [5 favorites]

You didn’t suggest you would, but just in case: I would not find a safe place and set it off. If you trigger it and it doesn’t go off you now have an armed and malfunctioning device to dispose of.
posted by Ookseer at 8:40 PM on December 14, 2022 [15 favorites]

I would call the police non-emergency number, and explain the situation to them. If it's potentially unstable, it may be safer for them to remove it from your property, instead of having you bring it in. Depending on the size of the police department, they may have their own Bomb Squad, who could deal with this.
posted by spinifex23 at 10:01 PM on December 14, 2022 [5 favorites]

I can think of few ways of defusing that thing. But you might also be able to call the fire department (or police) and somebody will come pick it up and probably just toss it into their pocket. I would probably just take it somewhere and set it off.

But I used to play with fireworks, including smoke bombs, and model rockets and such things. By the shape it's not meant to explode or anything. Pull the pin while holding the lever down, throw, spring loaded bit of metal held in place by the lever whips around and strikes a primer cap, that ignites a fuse that gives a few seconds of time before it goes off, then the fuse hits the bit that ignites the slow-ish burning stuff on the inside that produces the red smoke, but it's meant to burn slow and just make smoke. Mostly harmless.
posted by zengargoyle at 10:02 PM on December 14, 2022 [2 favorites]

"Long term I will take it to the police for disposal"
"Why not just take it to the police for disposal now?"

Please do not walk into a police station and say "I have a grenade"!
posted by EndsOfInvention at 3:31 AM on December 15, 2022 [12 favorites]

You call it a signal flare, not a grenade.

Are you anywhere near the sea?

Ships are required to carry red smoke flares for use as a distress signal. They expire after a few years and we have to arrange to drop them off at the nearest coastguard station for disposal. If you're anywhere near your local equivalent, they may be less surprised to receive it than the police.

Red smoke is universally recognised as a distress signal, so taking it somewhere and setting it off is not a great idea and may result in emergency services being called out.
posted by automatronic at 3:32 AM on December 15, 2022 [5 favorites]

Call the police and let them take it away and destroy it. FULL STOP.

As cool as it is, it's not designed for a 50+ year shelf life -- and you don't want to find out the hard way that it isn't immortal.
posted by wenestvedt at 4:14 AM on December 15, 2022 [3 favorites]

Response by poster: Well, it seems that the consensus is to get rid of it stat. BTW, thank you Dip Flash for pointing this out in the other thread, I'm a pretty safety conscious person and for some reason it never occurred to me that this thing could potentially self ignite. With the holidays and whatnot, I don't think I'm going to drop everything to get rid of it, but I will move it and the safe outside, and plan on calling the fire dept first (on the theory that they're less likely to over react and shoot me if I bring it in.)
Best answer goes to Dip Flash for taking the time to point this out in the other thread.
posted by Larry David Syndrome at 4:35 AM on December 15, 2022 [2 favorites]


I think it's the primer/fuse that gets unstable.

Out here in the suburbs our town fire department had me soak an old (presumably unstable) road flare in a bucket and the put it in the trash...but I think for a smoke grenade, they would respond with more alacrity.

Thank you for doing the right thing.
posted by wenestvedt at 7:32 AM on December 15, 2022

From a firefighter: please do not show up at a fire station (or any other public building) with anything that looks like it could potentially explode. That is how you cause an evacuation.

The advice I recommend is calling the non-emergency number for public safety and giving them all the information. Don't be surprised it they still take the precaution of treating this as potentially live ordinance. That's what we would do until we were absolutely confident that it doesn't represent a risk.
posted by itstheclamsname at 8:54 AM on December 15, 2022 [8 favorites]

Fun fact: my grandfather was a chemist working for the government in the late 1930s and through WWII. One of the projects he worked on were colored flares.

I'd never had a visual on what a signal flare looked like, so this was a really neat thread, thank you!
posted by annieb at 3:08 PM on December 15, 2022 [2 favorites]

It's almost certainly complete safe and inert - this is a flare, not a grenade and the most likely situation is that, if you try to set it off, it will just sit there looking at you and say 'you feel like picking me up to see what happens?'.

But, almost certainly is not good enough with a flare - if it does decide to ignite all by itself, almost nothing will put it out and that could well cost you your home.

I agree with those saying not to take it in anywhere unless you like being crash-tackled. Call the fire brigade and ask them what to do, then do what they tell you. Don't move it any more than you already have because that's the most likely thing to make it wake up.
posted by dg at 5:33 PM on December 15, 2022 [1 favorite]

I've set a lot of those off in my foolish lifetime, so the first thing I'd say is that if it ever goes off on its own it will be messier than you can ever imagine and could easily start a fire, they generate a lot of heat.

Like someone else mentioned, these are inordinately fun to set off, and not very risky in and of itself, so if you have access to an open field or some place private outdoors NOT IN AN URBAN AREA then go at it, just know that once it starts putting off smoke it wont stop for a good little while.

If you are afraid to touch it then simply call your local police department and explain to them that you have a smoke flare or smoke grenade that you found and they'll come and pick it up on their own terms, no harm, no foul.

Aside: I brought a bunch of these and other pyro home after an exercise once (20+ years ago) so I could demo them with some friends on a camping trip. i was scared shitless it would go off in my pack (stored them in an ammo box) but of course they didn't. Everything you use in the military is 100% louder and scarier when you aren't using it in a military situation is the main take-away I have to share on that topic.
posted by furtive at 2:16 PM on December 17, 2022 [1 favorite]

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