This Black Diamond AvaLung Bachpack is in very good condition and is a simple filtration device that draws air directly from the snowpack in the event of a full burial. Even dense avalanche debris consists of approximately 50% air that the AvaLung membrane is able to extract from the snow while removing exhaled CO2 away to help reduce the chance of an ice mask from forming around the mouth and nose. And while the AvaLung is an excellent tool to add to your backcountry safety kit, it should always be paired with a shovel, beacon, probe, knowledge, and experience partners that can rescue in the event a slide occurs.