Comments on: Avalanche Air Bag Backpack – Use One or Not? http://www.wildsnow.com/3736/airbag-overview/ Backcountry Skiing Weblog Blog, FAQs, more, links and info about randonnee, telemark and backcountry ski mountaineering. Sat, 25 May 2013 21:42:11 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Lou Dawson http://www.wildsnow.com/3736/airbag-overview/#comment-51535 Lou Dawson Mon, 25 Feb 2013 21:09:21 +0000 http://www.wildsnow.com/?p=3736#comment-51535 The last thing I'd do is mess around with guessing how full a cartridge should be. Just top it off. Lou The last thing I’d do is mess around with guessing how full a cartridge should be. Just top it off. Lou

]]> By: Charlie http://www.wildsnow.com/3736/airbag-overview/#comment-51532 Charlie Mon, 25 Feb 2013 18:44:43 +0000 http://www.wildsnow.com/?p=3736#comment-51532 (and, to that end, if the manufacturer specs a minimum useable temperature, I'd pay attention to that too.) (and, to that end, if the manufacturer specs a minimum useable temperature, I’d pay attention to that too.)

]]> By: Charlie http://www.wildsnow.com/3736/airbag-overview/#comment-51531 Charlie Mon, 25 Feb 2013 18:43:46 +0000 http://www.wildsnow.com/?p=3736#comment-51531 I'd imagine that the manufacturer expects the venturi to supplement an already full cartridge. A venturi will let them use a smaller cartridge, so they're going to exploit it almost as much as they can. Unless the manufacturer specs a minimum fill, I'd top it off. As for temperature, the relevant units are Kelvin. Room temperature is ~300 K. -40 degrees C/F is 233 K. At fixed pressure, the volume of a gas is proportional to absolute temperature. So, by volume, the cartridge will generate 22% less "air" at the coldest temperatures almost anyone might be interested in skiing. I'd be more worried about the bag material cracking at -40 degrees, or the valve assembly failing in some way, than any inflation issue. I’d imagine that the manufacturer expects the venturi to supplement an already full cartridge. A venturi will let them use a smaller cartridge, so they’re going to exploit it almost as much as they can. Unless the manufacturer specs a minimum fill, I’d top it off.

As for temperature, the relevant units are Kelvin. Room temperature is ~300 K. -40 degrees C/F is 233 K. At fixed pressure, the volume of a gas is proportional to absolute temperature. So, by volume, the cartridge will generate 22% less “air” at the coldest temperatures almost anyone might be interested in skiing. I’d be more worried about the bag material cracking at -40 degrees, or the valve assembly failing in some way, than any inflation issue.

]]> By: Nick http://www.wildsnow.com/3736/airbag-overview/#comment-51530 Nick Mon, 25 Feb 2013 17:50:15 +0000 http://www.wildsnow.com/?p=3736#comment-51530 I've fired off several airbags over the years with a less than full cylinder. At room temp, it's not a problem and completely fills. The problem is in colder temps, the air in the cylinder contracts and may not be enough. I’ve fired off several airbags over the years with a less than full cylinder. At room temp, it’s not a problem and completely fills. The problem is in colder temps, the air in the cylinder contracts and may not be enough.

]]> By: Chris http://www.wildsnow.com/3736/airbag-overview/#comment-51528 Chris Mon, 25 Feb 2013 17:07:54 +0000 http://www.wildsnow.com/?p=3736#comment-51528 I noticed in this write up that all of the airbags have a venturi valve. I have the Mammut Snowpulse pack and recently refilled my cartridge here at the local shop where they exhausted the air supply at nearly full. I was just curious how important it is to top off the cartridge with the venturi. Has anyone done any tests to verify inflation with a less than full cartridge? I noticed in this write up that all of the airbags have a venturi valve. I have the Mammut Snowpulse pack and recently refilled my cartridge here at the local shop where they exhausted the air supply at nearly full. I was just curious how important it is to top off the cartridge with the venturi. Has anyone done any tests to verify inflation with a less than full cartridge?

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