website describes their product as,
"In the event of an avalanche, the air stored in the high-pressure cylinder is released by simply pulling the handle. A combination of compressed air and a Venturi effect inflates the airbag in just 3 seconds.The inverse segregation phenomenon means that, all other aspects being equal, large objects tend to move upwards during mixing. Consider a can of mixed nuts, during shaking a peanut can fall into a small space created underneath while a large brazil nut cannot; so the large nuts "float" to the top over time.
Once the airbag has been inflated it protects the victim from shocks while simultaneously pulling them to the surface thanks to the inverse segregation phenomenon."
Airbag makers are claiming this also applies during the mixing of snow and rocks during an avalanche but I fail to see how the airbag makes a person that much larger. I find it more believable that the airbag lowers your total density making you more likely to "float" upwards (but that's not called "inverse segregation").
If you enjoy off trail mountain hiking and skiing consider an airbag backpack. But be warned they are not cheap. Costs have recently come down to $600 to $1,000.