How Do They Work?
All avalanche airbags regardless of brand work on the principle of Inverse Segregation or Inverse Grading. It states that if you shake a selection of shapes, the larger ones will rise to the top, even though they may be heavier. The principle is well proven and also known as the 'Brazil Nut Effect'. In a bag of mixed nuts, the Brazil nuts will always be on top. In an avalanche, it's best to make yourself like a Brazil nut.
The airbag itself is either packed into the top or shoulder straps (or both) of a pack and connected to a cylinder of compressed gas (air or nitrogen) or, in the case of the Black Diamond Jetforce packs, a high powered fan. The airbag is triggered by the wearer pulling a handle connected to one of the shoulder straps. All designs incorporate a stowable trigger handle which releases the gas inside the cylinder to fill the airbag. The airbag has a greater volume than the cylinder, with the extra air volume supplied by air drawn into the system using the 'Venturi Effect'.Airbag Shapes.
The airbags stocked by Facewest come in 2 basic shapes. The Mammut Protection (also original Snowpulse Lifebag) shape which provides side protection to the head and to the front of the chest whilst still leaving the user completely free to carry on skiing or boarding to try and get out of trouble. The other shape is generally known as the 'Wings' shape, these airbags just extend behind the user and is there to provide the volume for inverse segregation rather than also providing extra protection. Whilst the Mammut Protection shape does provide the best protection, the fact that the arm straps contain the airbag means they are thicker, heavier and less flexible than a standard pack. The Wings shape means the shoulder straps of the pack are more like a general pack, and offer a less complicated construction, but do not protect the users head as much. As the primary function of the airbag is to offer extra volume all systems work well.
Rapid Airbag Inflation
Battery Or Compressed Gas?
The Airbag market is now divided into two categories; Electric battery inflated or compressed gas inflated airbags. Each type has its pros and cons and the right bag for you will depend on your anticipated use.Compressed Gas Airbags
Compressed gas Airbags like the Mammut & ortovox models rely on a compressed gas cylinder which is screwed into the airbag unit and punctured when the activation handle is pulled. Resulting in rapid inflation of the airbag itself. This technology has been around for nearly 20 years now is is pretty mature. Ortovox & Mammut have both got the inflation system itself down to very light and compact units which are currently smaller and lighter then battery operated systems, giving you more room in your pack for kit.
Airbags system cylinders can be filled with either Nitrogen or compressed air. To the user there isn't any noticeable difference. Once discharged Non Refillable cylinders used by Mammut need to be exchanged with a suitable dealer. You pay a small charge, currently £30, and exchange your empty cylinder for a full one. This is best done in person in the local resort or town if possible or can be done by post once you are back in the UK. Mammut and Ortovox now only offer a carbon non refillable cylinder rather than an option of a carbon or steel one. Carbon is much lighter than steel and the price is now the same as the steel ones once were.Battery Inflated Airbags
In the past 5 years electric battery inflated airbags have been making huge advances. They are now much smaller and lighter than the first generation versions, and now come in two versions. The Black Diamond Jetforce packs which use a large rechargeable Li battery that you can get four inflations from. The Alpride airbag system which is used by Scott & Osprey uses a capacitor which charges off 3 AA batteries and will give you one activation per charge. Electric packs offer much more flexibility but if you are having to charge your pack over and over for multiple inflations then you really need to reconsider the terrain you are on!. They are also muc heasier to travel with as they do not need compressed gas cylinders.Deflating Your Airbag.
After use on the hill, you will probably deflate your airbag and move to safer ground, check you know how to do this before you take your airbag out. The instruction manual that comes with your airbag or the manufacturers website are the best places to find out how to do this correctly.