If you're heading to the back country this winter season here are some gadgets--and the science behind them--to keep you safe.
It's ski season! The time of year when "suiting up" requires half-an-hour and a dozen layers, and when speed demons head to the mountains to fly down slopes on snowboards and skis.
Groomed slopes at ski resorts are pretty safe as long as you pay attention to signs and other skiers. But if you like to play on the road less traveled you have to be avalanche-aware.
If you're caught in an avalanche you want to stay as close to the top of the snow pile as possible, so that you can breathe and are easily visible to rescuers. Avalanche airbags self-inflate from a backpack with the pull of a cord and are designed to keep a person near the top of the mass of snow by way of a physics principal known as the Brazil Nut Effect. If you shake a tin of mixed nuts up and down, the biggest nuts (typically Brazil nuts) will end up on top. This is thanks to granular convection. As you shake the can up and down the base of the can pushes nuts upward. The sides of the can pull–using friction–the contents back down. This creates a flow pattern in the can: nuts move up in the centre, and back down on the sides. But with mixed nuts, not all the nuts are the same size. Once the big ones get to the top they don't get a chance to move back down; the spaces along the sides are too small, and are always being filled by smaller nuts. Avalanche airbags make a skier more like a Brazil nut. They make a person bigger without adding weight, and therefore you're more likely to be jostled to the top of the snow pile.
Did you know? If you are caught in an avalanche, try to remove your skis or snowboard. Having them attached to your legs can twist and break your limbs as the snow moves around you.
Although the initial impact of an avalanche can injure a person, 75 percent of deaths in avalanches are due to suffocation. Once a person is buried under the snow it is hard to get enough oxygen, even if you make yourself an air pocket. The key is getting rid of the carbon dioxide you exhale with every breath. Your warm breath can melt the snow around you just enough so that it will refreeze into a layer of ice. The ice traps carbon dioxide in while keeping oxygen out. A bad mix for our lungs.
An Avalung not only gathers fresh oxygen from the snowpack, it also gets rid of the CO2 you're breathing out. The device is like a snorkel, except that as you breathe out, the harmful hot air and gas is diverted to a tube that opens behind your back. Clean air in front, carbon dioxide behind.
Did you know? To preserve oxygen you should only shout once for help when you are initially buried. Then wait until you can hear rescuers nearby. Snow is such a good insulator that they wouldn't be able to hear you until you can hear them anyway.
These two great inventions help increase your chances in an avalanche, but your rescue still relies on how fast someone can dig you out. Always go down slopes one at a time, with your friends watching from a safe distance. That way if an avalanche occurs, you won't all be caught in it. And while airbags and the avalung are amazing high-tech tools, you should always be carrying a good old fashioned shovel too.
National Snow and Ice Data Center
Avalanche gear review
Brazil Nut Effect demonstration
Suffocation leading cause of death in avalanches
Brugger, H. & Falk, M. (2002). Analysis of Avalanche Safety Equipment for Backcountry Skiers. Austrian Association for Alpine and High Altitude Medicine. Translated by Genswein, M.
Radwin, M., Grissom K., Scholand M., and Harmston C. (2001). Normal oxygenation and ventilation during snow burial by the exclusion of exhaled carbon dioxide. Wilderness & Environmental Medicine. v. 12 (4) p. 256-262
Article first published December 2, 2011