The idea is pretty simple: don鈥檛 get buried. Air-bag-equipped backpacks (we review four on the opposite page) are designed to boost the wearer鈥檚 overall buoyancy, vastly increasing the chances he or she will end up at or near the surface of the debris field when the avalanche comes to a rest. To deploy, just pull the pack鈥檚 trigger handle, and a 150-liter air bag made from heavyweight nylon bursts from the pack, inflating in two or three seconds with compressed gas鈥攖he same stuff used in scuba tanks and paintball guns. Once inflated, the bag also helps protect the wearer鈥檚 head, neck, and back from collisions with trees and rocks.
1. Trigger: The air bag is triggered using a handle protruding from one of the shoulder straps. (Think hydration hose; you can also tuck it away when you鈥檙e not in avalanche-prone terrain.) When the device is armed, a firm tug releases a pin or small explosive round, unleashing the contents of a 3,000 psi air or nitrogen canister.
2. Reinforcements: Air-bag-equipped packs are up-armored in various places to ensure they stay put (and intact) when activated. The material is heavy-duty and reinforced in key areas with ultratough fabric like Cordura. Shoulder and hip straps can support anywhere from 650 to 1,000 pounds of force; buckles are often metal. Leg loops keep the pack from riding up.
3. Air-bag configuration: Packs with ABS systems (including those made by Dakine, Mountain Hardwear, the North Face, and Ortovox) have two independent bags that inflate from the sides like wings, for redundant safety in case one gets damaged or doesn鈥檛 inflate. All others deploy a single, pillow-like bag similar to the one shown above.
4. Canisters: Compressed-air canisters (used by everyone but ABS) can be refilled at dive or paintball shops, specialty ski stores, or REI. ABS鈥檚 nitrogen canisters must be sent to the company or exchanged at an ABS dealer. Note: the TSA doesn鈥檛 allow you to fly with full, pressurized canisters. Consult for more information on flying with and refilling canisters.
