Just how dangerous is it to refill fuel canisters?

Question

In the past, it was possible to refill MSR canisters if you brought them into their repair shop in Seattle. However the repair shop has been closed under the excuse of COVID and still hasn't reopened despite Washington dropping all COVID restrictions on June 30th. I've asked REI employees if they know of an alternative refill location but they weren't able to help me, so it seems like the only remaining option is to keep buying new cans.

With this in mind, I wanted to start refilling my own canisters to avoid creating unnecessary garbage while hiking. But just how dangerous it it? Are the warnings on canisters about refilling just there for "cover your ass"/legal reasons or do I risk having the can explode on me all of a sudden if I refill it too often?

NB: I can afford to buy these cans without issues but feel bad about throwing out perfectly good metal after a few days of camping. So this question is purely environmental rather than financial.

Update: I’m not looking for instructions on how to refill canisters (I already know how that works). Just interested in odds of something going wrong if I do this over a long period of time.

Answer 1

You almost certainly won't be able to find propane/butane/isobutane mixes for refilling. I'm pretty sure you'll only find pure propane and the backpacking LPG stoves are made to be the most efficient with these mixes. You could have worse boil times and less consistent pressure, unless you're using a regulated stove valve.

Pure propane will actually work to lower temperatures, but there's a good reason you shouldn't fill yourself. On the safety side, the 110/220/450g light canisters are made as light as possible and this works well with the butane derivatives. But propane needs higher pressure to liquify so it needs a much sturdier can. I wouldn't refill the 1lbs steel cans, but those are already safer to refill with propane. Add to this that the light cans are not engineered to be refilled manually and the valve assembly is not very sturdy. If debris gets in there, it might get stuck partially open because it's only spring actuated. The threading can also get worn if it's used over and over, leading to potentially dangerous leaks. The can also lacks any safety overpressure valve so if you overfill it, that will extert stress.

Answer 2

I'll focus on your final statement "So this question is purely environmental". As such my answer will be purely environmental and not on safety which I am unqualified to answer.

If you are refilling you are still buying other canisters/containers to refill the original canister with. So you aren't going from X material to 0 material but rather from X to Y with the hope that Y is smaller than X. If you really wanted to you could calculate the fuel/material ratio but it seems like Y can't be that much smaller than X. As such I'm not sure how much material it really saves the environment. Also, camping fuel canisters are made by companies that generally care about the environment. One example is MSR (chosen because it happens to be the brand I see in stores the most often and you mention them in your question), which documents their environmental impact in detail on their website. If you are buying a bulk brand fuel to use as refill there is a chance that company doesn't produce their goods with the same environmental standards.

You also need to obtain the fuel. Those canisters are available at many shops, such as REI as you mention, which have relatively efficient transportation methods to get the product in the store. If you are going out of your way to order/find the bulk containers then you just added to your environmental impact.

So while you might be using slightly less material as an end user, you might not necessarily be having a smaller environmental impact. So it isn't clear that what you are attempting is really any better environmentally. What was the original question again? :)

Answer 3

What this post is NOT: This post is not promotion or propagation of cartridge refilling. I do NOT promote cartridge refilling and I do not do it myself. I do NOT claim it is a safe practice.

Safety warning! Cartridge refilling is not safe even when you are careful.

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It used to be quite common around here in the past decades (say 1990s and 2000s) because the canisters were more expensive relative to the salaries. Therefore it was mainly done to save money. You can find tutorials in quite mainstream outdoor magazines in Czech Republic.

I never did it myself, nor did I ever knowingly use refilled canisters. With the exception of canisters bought in Leh in India which were probably refilled as half of them performed really bad and emptied very quickly.

Those who say it won't work are clearly wrong. Yes, there is more propane in those big canisters, but the mixture sold here will still work fine.

The key I always heard is to measure the weight of the refilled canister carefully and tu put in somewhat less gas than originally. The concave bottom of the canister is a safety measure. If it changes its shape or even buckles out, you clearly overfilled. Be extremely careful, empty the canister and throw it away.

I have not heard of a serious injury that would happen to a person doing such refilling, but I chose not to try it myself. The biggest risk is probably an explosion caused by over-pressurisizng the cartridge or explosion cased by a cartridge with a defect, no longer holding firmly together... That would probably be without fire, but the expanded gas could be ignited by some other means around. As spikey_richie correctly added, in the right concentration the ignited gas could explode at once possibly with catastrophic consequences, so it can only be done outdoors.

Answer 4

The basic problem with refilling such fuel containers is that they absolutely must not actually be filled. A "full" cylinder is not full, there's a certain amount of unused volume. Remember, most things expand as they get warmer--and that includes the fuel in those cylinders. If there isn't space for it to expand the best possible outcome is for a blowout to fail, very quickly venting all the fuel in a freezing but highly flammable jet.