Also be sure to check out our Avalanche Beacon Review. If you are in a situation where you are using an airbag, you probably also need a beacon.
How Do Avalanche Airbag Packs Work?
Avalanche airbags work because of physics and a process called inverse segregation. Simply put, this means that when shuffled, bigger particles tend to end up on the surface and smaller particles tend to end up on the bottom. For example, if you shake a box of sand and pebbles, the pebbles will rise to the surface and the sand will work down. The pebbles work their way up because they have more volume than the sand. In similar and more familiar terms, think of a bag of chips: The small chips work their way down, and the bigger chips work their way up; this is inverse segregation at work.
If you prefer a visual example of how airbags work, check out the movie below:
Jonathan Shefftz compiled information from five separate studies and published them in the April 2012 issue of The Avalanche Review. While these studies are mostly older, primarily European studies where people don't typically ski trees as much as we do in North America, he found fairly similar numbers. These studies show that wearing an avalanche airbag could possibly save a little more than half of those who would have otherwise died. Here is an excellent video of Bruce Tremper of the Utah Avalanche Center discussing avalanche airbag statistics. Bruce Tremper
Our view at OutdoorGearLab is that saving roughly half of those who would otherwise die in avalanches is pretty good; however, you shouldn't change your approach to terrain or let wearing one alter what terrain you are willing to travel. An airbag pack certainly doesn't take the place of proper training. Why? Because a 50% decrease in dying is pretty good, but you still have a 50% chance of dying
The overall non-inflation rate from an in-depth study recently completed by Pascal Haegeli with Simon Fraser University in British Columbia was an astounding 20 percent — 61 of 307 people who were involved in an avalanche had packs that failed to deploy or they chose not to deploy. This percentage is close to the rate reported by Brugger in a similar 2007 study. What are the causes for these non-inflations? Haegeli's data gives these likely reasons:
60% deployment failures by users
12% maintenance errors (e.g., canister not attached properly)
17% device failures (i.e., performance issues, faulty design)
12% destruction of airbag during involvements
A Note on Wearing an Avalanche Airbag Pack
In the backcountry, wearing an airbag pack without a beacon is unacceptable. Airbag packs reduce the chance of burial in an avalanche, but if you do get buried, you have a negligible chance of survival without a beacon. Being caught in an avalanche can be 50 times worse than being hit by the gnarliest ocean wave you have ever experienced. It's an incredibly violent experience; you'll have no control of your body and won't have any idea of what way is up. When you do wear an airbag pack, the leg harness strap is a must. While dorky, it plays a large role in keeping your pack on your body. Lastly, when entering or approaching avalanche terrain, have the trigger out and ready to use. There have been several high profile accidents where the victim had an airbag pack on but didn't have the trigger out and ready to pull. Still, the number one reason backcountry travelers die while wearing airbag packs is trauma, not being buried while wearing one.
How Do Avalanche Airbag Packs Work?
Avalanche airbags work through a process called inverse segregation or the "Brazilian Nut" effect. Inverse segregation is a law of physics where bigger particles work their way to the surface and smaller particles work their way to the bottom. By wearing and deploying your airbag, it makes you an even bigger "particle" than you would have been otherwise. If you shake a box full of sand and rocks, the rocks will rise to the surface and the sand will work its way below. The rocks work their way up because they have more volume than the sand grains. Sometimes people think that the airbag helps you "float" based on the same principle that would cause an airbag float in water. But that principle is different: an airbag pack would help you float in water by increasing your volume (inflating the bag) without adding any mass (not making you heavier). This concept is easier for most people to grasp but it is not the same principle as applied to airbag packs.
The video below shows how the airbag works:
What the Critics Say
With some amazing survival statistics and a few high-profile accidents, avalanche airbag packs are dramatically increasing in popularity. Skeptics say that airbag packs will affect back-country enthusiasts' decision-making, prompting more risky behavior. But that's also what people said about beacons when they first appeared and now they are considered standard backcountry tools. If you are going into the backcountry, an airbag pack is NOT a replacement for a beacon. Airbag packs hopefully won't affect a wearer's decision-making with respect to risk and users hopefully won't ski or snowboard an area they normally wouldn't.
A Little on the Statistics
Some studies originally done by ABS and the Swiss government claimed 97 percent positive outcomes out of over 220 deployments. While this statistic is true, the way it is most often presented is misleading. First off, around 81 percent of people caught in avalanches survive. Of those 81 percent, it's not clear how or why they survived. Was the avalanche very small, were they saved by their companions with beacons, were they straight up just lucky? Of the 19 percent that died worldwide, 1 in 4 died from trauma. Some speculate that number is higher, 1 in 3, in North America because we do a lot more tree skiing. Trauma is often a result of hitting a tree, going over a cliff or some other kind of high-speed impact, in which case most airbag packs will generally have little effect on the outcome. The other 75 percent of avalanche fatalities come when the victims die from asphyxiation. This is a result of breathing out carbon dioxide to the point that it completely surrounds your head and you aren't able to get enough oxygen. Airbags help by preventing the wearer from being buried so they avoid asphyxiation. Also, even if the wearer is buried, they will be closer to the surface (or maybe have a visual clue connected to their body) that leads to a shortened rescue time, increasing their odds of survival. In an American Avalanche Association study that included 422 completely buried victims (but not people who died from trauma), it was found that when people buried in an avalanche are dug up in the first 15 minutes they have just over a 90 percent survival rate; at 20 minutes it's closer to 60 percent, and at 30 minutes it's below 40 percent. There are several studies going on now to amass statistics on how many people are saved by airbag packs. Snow safety professionals say that out of 100 avalanche fatalities, somewhere between 35 to 70 more people would have survived. Regardless of which numbers you believe, even the biggest skeptics agree that deploying an airbag when caught in an avalanche will strongly increase your odds of survival.
Things to Consider When Looking at Airbag Packs
Where and How Are You Going to Use Your Airbag Pack?
When we ask what kind of back-country skiing and snowboarding you will be doing, we are referring to heli skiing, cat skiing, side-country, pure touring, ski mountaineering, hut-to-hut trips or a combination of these. Choosing what you will be doing will highlight features to consider more important than others.
With heli and cat skiers and snowboarders, you won't need to carry much, and having a smaller pack that rides better with you is more advantageous than one with more volume or pockets. The ski/snowboarding carrying system doesn't have to be good (or even exist at all) because odds of you having to strap your skis or board to your pack are slim. Most cat and heli skiers either choose airbag vests or very small packs, generally under 15L but up to 25L if you want your airbag pack to be a little more versatile.
Side-Country or "Slack-Country" generally refers to skiers and snowboarders who access the backcountry or out-of-bounds zones via a ski resort. These areas are generally accessed by skiing under a rope or through a gate. It can also include a fair amount of booting and possibly even skinning. Many side-country skiers look for packs with a volume of 15-30L, though some go even smaller. Most side-country skiers want a pack big enough be able to carry all of their equipment, a few extra layers and ideally have a pretty good diagonal ski or snowboard carry system. Very small packs (less than 5L) or airbag vests can work but are often a too small for everything but the shortest side-country forays.
Backcountry touring refers to skiers and snowboarders who go out for a whole day or longer and generally access the backcountry by skinning. Most backcountry tourers look for packs 20-40L. While some people occasionally use smaller than 15L packs, this takes some practice and will require some sacrifice. OutdoorGearLab friend Eric Dalzell used an ABS pack on more than half the touring days of a 15-day ski touring trip to Alaska's Chugach Range, but it was a struggle. Having a solid ski/snowboarding carrying system is key because unlike a lot of side-country boot packing, the ascents are often longer and carrying skis over your shoulder often impractical and painful.
For hut-to-hut and multi-day trips, most of the features you want are similar to that of a day touring pack, with only a few small changes. One is volume for self-supported trips like the Spearhead Traverse or hut-to-hut trips like the Haute Route. Most people will need at least a 30L pack and a closer to a 40L for self-supported trips. Weight also becomes an issue because you likely have to carry more stuff. If you go on multi-day ski tours to have fun, then skiing a long distance with a heavy pack tires your legs quickly, makes funky snow even worse and is just generally not fun.
Nitrogen vs. Compressed Air
Compressed nitrogen is less affected by temperature and will perform better in colder temperatures than will compressed air. Another advantage of compressed nitrogen is that it can be stored in a smaller canister to help save space in your pack. The big disadvantage of compressed nitrogen is that it is more expensive and difficult to refill. The ABS system works by puncturing the canister with a little copper disk so you need to replace the canister after each deployment. Several backcountry shops and heli-ski operations offer a cartridge swap program for around $40-$70. But if you fly to a remote place that can't perform a swap, you need to plan ahead. This is where compressed oxygen has a huge advantage. Compressed air canisters can be refilled at most scuba or paintball shops and even some fire stations for a cost of around $5-$20. Also, with ABS if you can't find a place to swap your cartridge it can take a disappointing 3-6 weeks for them to return it. ABS, Ortovox and The North Face use compressed nitrogen and Mammut, BCA and Snowpulse use compressed air.
Avalanche airbag packs are expensive. For most people, they are the most expensive backpack or piece of safety gear they will ever purchase. Also, airbag packs have one of the bigger price ranges of any piece of backcountry gear. You can spend anywhere from $1300 on the ABS Vario 40 or as little as $500 on a Float 22 plus a canister ($175). Regardless of price, all the airbag packs we reviewed are time tested.