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I use pierceable butane canisters for cooking outdoors:

enter image description here

Given that butane boiling point is 30 to 34 °F, is it safe to punch a hole in the canister when the outside temperature drops below 30 °F and transfuse the liquid butane to another canister?

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No.

The butane will vaporize below the boiling point, just as water vaporizes below 100°C.

  • I forgot to mention at 1 atm pressure at sea level. What makes you think that water vaporizes below 100°C at the aforementioned conditions? There may be some moisture on the walls, but certainly no serious discrepancy of pressure above 1 atm in a closed water canister below 100°C. A closed hot coffee thermos flask is a good example. Sorry, but I don't agree with you. – dimachaerus May 26 at 3:00
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    @dimachaerus you need to learn about vapour pressures, and consider when the vapour pressure of butane is enough to be flammable. You could pour it, but you'd lose a fair bit, and that's a hazard. But why would you want to? – Chris H May 26 at 6:53
  • I think the way butane is contained into one-use canisters as in photo is at low temperatures when it is liquid, so there is no extra vapor pressure at the same low temperatures. To answer your second part suppose there is a faulty screw and valve of the apparatus using the canister in question. Isn't it safer to pierce it when the temperature is below boiling point? – dimachaerus May 26 at 8:21
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    Safer yes, but not necessarily safe. Since you are just below boiling point for butane, a good example would be water at 95 degrees. There will be significant evaporation. – Jasper May 26 at 11:42
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    In a closed box, you are right. But when you are pouring things, boxes will not be closed. – Jasper May 27 at 16:44
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No. There is a safety system in the newer C206 canisters that should prevent you from emptying a pierced can, unintentionally or not. It remains to be found if this works at low temperature and pressures though.

However, the C206 GLS cartridge has a new integrated flow reducing system, the Gas Lock System, which is compliant to the new European standard EN 417:2012 legislation. The system prevents the majority of residual gas from escaping the cartridge when accidentally disconnecting it from the appliance, thereby also preventing flare-ups

Bear in mind, it is more than likely you'll find some C206 canisters filled with a butane/propane mix (the can pictured in the question shows one of those, note the dutch butaan/propaan mengsel on the can) and since propane's boiling point is a whopping -43°F (-42°C), you'll certainly trigger the safety system when it starts escaping.

  • Yes, I am aware of this, you rarely find butane/propane canisters (and if you do they are only 80%butane- 20% propane) because of this danger. – dimachaerus May 29 at 13:37
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    Just so you know, isobutane/propane mixes are pretty much the only thing you find in North America. What danger do you speak of? – Gabriel C. May 29 at 13:40
  • The danger is the higher pressure of propane at normal temperatures. Requires canisters with thicker walls. – dimachaerus May 29 at 17:02
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    There's no danger involved in this at all. Those canisters are perfectly capable of handling the winter mixes inside. If you're from Europe, the real reason you don't see many winter mixes is that most of continental Europe is a very mild climate and as such the more expensive fuels that work in colder conditions aren't in as much demand. Snow Peak (Japanese), MSR (American), and Primus (Swedish) only produce (iso)butane/propane mixes. Primus make 3 grades for different conditions, but there's always at least 20% propane minimum in exactly the same canisters. – Gabriel C. May 29 at 18:20
  • Yes, thanks for the clarifying this. Makes perfect sense in the Arctic climates, otherwise there would be no gas to ignite at those temperatures.The butane turns all to liquid... Still, propane alone is never used in these canisters. They can't withstand the pressure. – dimachaerus May 29 at 19:26

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