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Monday, March 19, 2012

Canisters, Cold, and Altitude: Gas in a Nutshell

OK, so here's the deal on canisters in cold weather and at higher elevations, in step-by-step form:

1.  Choose good gas.  For weather below 50°F/10°C, avoid butane mixes. Get an isobutane mix.  I've got all the major US brands sized up on my blog in What's the Best Brand of Gas for Cold Weather?  Above 50°F/10°C, it typically doesn't matter what brand or blend you buy.

2.  Know your limits.  Canisters containing isobutane mixes work reasonably well down to about 20F/-7C at sea level throughout the life of the canister if you use good gas (see item #1, above) and good technique (see item #4, below).  Now, that's just a number, which isn't a bad number if you just want the short version, but if you want to know more about that number, how I came up with it, and how to plan using it, see Gas Stoves: How Cold Can I Go?  Canisters get colder as you use them (canister "chilling") which can negatively impact performance.  See item #4, below, for how to compensate for canister chilling.

3.  Adjust for Altitude.  The higher you go, the lower the outside pressure.  The lower the outside pressure, the colder you can operate a canister gas stove.  You receive approximately a 1F per 1000' of gain colder advantage (about 0.5°C per 300m gain).  The idea that canister gas stoves don't work well at altitude is a myth.

4.  Use good technique.  Basically, start with a warm canister and keep the canister warm.  For "best practices," see Cold Weather Tips for Gas Stoves.

Now, in the above, I'm speaking primarily about "regular" gas stoves, the kind that screw right on to the top of a canister.  If you have a remote canister stove that is capable of inverted operation (see my Stoves for Cold Weather II article in Seattle Backpacker's Magazine for more information), then the limit in item #2, above, changes from about 20°F/-7°C to about 0°F/-18°C.  All of the other items still typically apply.  If you want to go out in weather that is that cold, I strongly suggest you do your homework, part of which should be to read Gas Stoves: How Cold Can I Go?

There, in the proverbial "nutshell," is how to deal with cold weather and adjust for altitude for canister gas stoves.

HJ

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6 comments:

  1. The impact of altitude on gas stoves is new to me, but makes sense - thanks!

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  2. You're welcome. Of course at altitude things can be really cold and windy, but there's nothing about gas per se that prevents it from functioning well at altitude.

    HJ

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  3. I have messed around with various stoves and fuels for years. You summed up the critical factors for a gas canister stove well here. I'm now using a MSR WindPro most of the time. It is possible to invert the canister and I find that works well even in freezing weather.

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  4. Hi, Pliny,

    Thanks. Yeah, a WindPro does a pretty good job in cold weather if you invert the canister. I've been pretty happy with mine.

    HJ

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  5. Thanks for the help so far. I took a small Primus Gas stove with Coleman Butane/Propane mix on a short hike a couple days ago to altitude 1500m in snowy weather and about -10C. Stove worked well at first and then faded quickly before coffee was ready! Shaking the stove gently brought back a fiercer flame which faded again. It did the same thing back at home in the kitchen ( 500m above sea level ) - maybe I have another problem altogether. I'll check your pages again in more detail. Happy Hikin'

    Pondlife

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    1. I'm assuming that your kitchen was much warmer, yes? A fresh canister of Coleman should work well down to about -18C, but like all canisters, it will "fade" with use. Use a) depletes the propane which is what drives the pressure in cold weather and b) use itself causes the canister to get colder than it's surroundings. Both "a" and "b" wil make your flame decrease in size. In your kitchen it should have warmed up and started working again.

      Next time you're out and it's cold, try putting the canister in a pan of warm (NOT hot) water.

      HJ

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