Let me say first that I agree with you on the risks and I personally wouldn't do it myself. And I applaud you in your efforts to warn other people. But at that point I would say it's up to the individual to decide if they want to use it. I wouldn't recommend inflating your car tires to twice the rated pressure, but I don't think air compressors should be limited to 40 psi just to avoid the potential problem. You can't protect everybody from their own stupidity, it's up to the individual to know the risks.

To play devils advocate, you state "I believe they can be refilled safely -- just not with 100% propane". I'm sure there are some people who think that there's enough safety factor in the canisters to fill with propane, then on the opposite extreme you'll have people who say it's not safe to refill at all, even with butane. Who's right? Unless someone can come up with data to support their position, it's all just feeling. You probably knew all the risks involved before you bought this contraption, yet you wanted to try it for yourself. I think other people also have the right to make their own decisions about it.

EDIT: I actually re-read you post and am confused. Did you actually buy this device and try it out for yourself?

OK, good example. But say you pulled into a gas station to fill up your tires with air and the compressor at the gas station shot your tires up to double normal in a split second. Safe compressor or unsafe?

I think most people would say that, for filling tires, it's better to have a compressor that is a little slower.

So, I agree with you that we shouldn't approach life with the equivalent of a 40psi cap on everything we do -- but there are safe ways to do things and there are unsafe ways. A compressor that shoots your tire pressure up over double normal inflation in a split second is probably not a compressor that the vast majority of us would want to use to fill our tires.

Likewise, I agree, there are people who will have reason to put propane in canisters not rated for propane-level pressure. Cold weather hunting or backpacking comes to mind. So long as you exhaust the canister before you bring it into a warm environment, you should be OK.

But would this device be the way to do it? To my mind, no. This device is so shoddy that I wouldn't use it even if I thought the application were appropriate.

Heck no! I wouldn't want to be within a quarter mile of this thing if it were in use. I'm not afraid of canister refilling if intelligently done. I'm not even afraid of using propane if intelligently done. I'm afraid of this device and of the directions the seller lists with this device. Who in their right mind uses aquarium tubing to transfer propane!?

HJ

Thanks for the heads up. I have a different device I bought through a catalogue, much different than what you have shown. Never had a problem but now I'm a lil concerned with the cannisters I have at the cabin.

Interesting. Do you have a photo?

What kind of canister did you refill, what did you refill them with, and were you careful to only fill to their rated weight limit?

First, the most critical thing is to note how much a full canister weighs when you bring it home fresh from the store. When you refill, NEVER exceed this weight. Overfilling can lead to dangerous pressure levels inside the canister. If you forgot to weigh the canister when you brought it home, you could weigh an empty canister and add the net weight printed on the canister to derive your max weight, but I think weighing a fresh canister is the better option; it avoids any potential math errors.

Second, know what type of canister you're refilling. Is it a 100% butane canister? Is it a butane blend canister? Is it a 100% propane canister? Different canisters can accommodate different gasses, and you need to know which type you have.

Last, only refill with a gas or gas blend with a vapor pressure that is equal to or less than what originally came in your canister. Do NOT refill with a gas or gas blend with a higher vapor pressure. Generally, refilling with 100% butane is relatively safe (as safe as canister refilling gets anyway) because 100% butane will always have equal to or lower vapor pressure than any combination of the gasses typically used to fill canisters (butane, isobutane, and propane).

You can get some idea of what's going on with various blends by looking at the following chart:


Note that the above chart lists propane and butane only. Isobutane is not listed. Vapor pressures with isobutane will always be higher. So, that chart can give you some idea with propane and butane, but don't use that chart for isobutane. You'll need to look elsewhere for that information.

HJ

Assuming I survive, the first thing id be thinking is where can i get one of those compressors? On a somewhat unrelated but equally dangerous topic, i have read of people using their spare tires as an air tank, filling them to 80-105 psi. I dont know if it was a widely used practice, but it seemed fairly common to read about it. Again, not something I would do, but it's one of those things that many people have done without dying. So while a compressor like that could be dangerous, I wouldn't see the need to have it removed. Maybe a warning sticker or something

I will admit I was curious about the product you showed so I looked it up on eBay to see how much it was. One thing I noticed was that it never really said it was used for refilling propane, only liquified gas. There is a picture in the ad of some sort of blue bulk gas canister, but I can't read the writing on it because it's in Chinese. When I looked closer at the picture, I'm not even sure if it's even possible to connect this hose to a standard propane tank, at least not to the common type of propane valves that we use in the US. Are you sure this isnt a butane tank refiller that is meant for the overseas market?

Depends on the spare, some donut type is actually designed to run at very high psi, something around 80.

The product was for sale on US eBay. In the US, that connector attaches to "bulk" propane tanks.

HJ