Snowpulse avalanche airbag backpacks (what are these?) were the first to provide a user refillable air cylinder. This feature allows you to refill your spent cylinder and get back on the slopes without delay or shipping costs, and if you don’t want to refill it yourself, you can always exchange it for a full one through the mail. My fiance has had a Snowpulse for a couple of years and we’ve refilled it several times (no she didn’t use it in an avalanche, just for regular tests). Snowpulse is coming out with a new system (2.0) next season, which is similar to that described below, but more user friendly. While the current system may appear complex, once you’re used to it and have a good place to get the compressed air, you can do a refill quite easily. Old 1.0 or new 2.0 system, below will give you an idea of what’s involved in a refill. For our reports on this process for other brands, please see our index of Avalanche Airbag blog posts.
Rachel models her inflated Snowpulse airbag. Now that it's been triggered, we'll need to deflate the bag, repack it, and then refill the air cylinder.
To deflate the bag, you'll need to use this little stick which is attached to the inside of the backpack by a cord.
Push the stick up into the valve as shown and leave it there as you sit on the airbag to deflate it.
Once the airbag is deflated, you can start to repack it. First, you must slide the zipper which was forced open when the bag inflated back to opposite shoulder strap.
Fold the bag as shown in the included directions into the shoulder straps and begin to zip it up. It's not too difficult, as there is plenty of space for the bag to fit, but the sequence and folding methods take a few times to remember and master.
Once the airbag is put away, you'll need to disconnect the cylinder. It is screwed on in two places, the main air attachment (upper) and the release pin cable attachment (lower, attached to the red part).
Unscrew the one attached to the release pin housing first. When this is off, you'll see that the release pin is still attached to the cable but possibly far down inside the cover. Get as much cable slack as you can by pushing the trigger handle on the shoulder strap up. However, you may be unable to reach the pin. If so, very carefully use a pair of pliers covered with cloth, as you don't want to scratch that pin.
Now that the pin and cable have been pulled past the cover, unscrew the pin and save it for later. Then you can unscrew the cylinder from the air hose.
The tools needed for the procedure. Included in the refill pack are: (B) tweezers; (C) spare release pin incase you lose the original; (D) grease; (E) plastic cone to help putting on the o-ring (I don't find it necessary); (F) stickers to seal the main air outlet on top of the cylinder head x10; (G) stickers to seal the housing x10; (H) bag of o-rings x10. (I) and (J) are protective caps that come with the cylinder (A). Additional tools needed are: (K)SCBA adaptor for firestation (or a SCUBA adaptor if using a dive shop); (L) 19mm cone wrench; and (M) pliers which are sometimes necessary to get the release pin out of the cable cover on the pack. If you do this, BE SURE TO PROTECT IT WITH A CLOTH, as you don't want to scratch the release pin!
This is what a spent Snowpulse cylinder looks like. Note the little red sticker on the far left- it has a hole in it, that's where the air escaped into the airbag. The release pin is lying to bottom right, it was pulled from the piston housing, which caused the piston to shoot out of position, releasing the air and pushing the lever through the big red sticker (in the middle, the lever left a tear in it).
Unscrew the piston housing using wrench (not included). I find that a 19mm bicycle cone wrench works well, but you can also use a crescent wrench attached to the main part of the housing body.
Tear off the red sticker from the piston housing (and the one from the top of the cylinder head)
Pull out the piston from the housing. During all steps, take care to not scratch it, as you don't want a leak.
Remove the o-ring using the included plastic tweezers or a toothpick. Don't use anything that could scratch the piston. Discard the o-ring, even if it looks fine.
Use the included grease to grease a new o-ring.
Push the new o-ring onto the piston. Then grease the piston.
Reinsert the piston into the housing (o-ring side out). Notice how as you push the piston in, the lever swings out. This lever will need to be pushed in so that its hole lines up with the hole for the release pin.
Use the release pin to push the lever back in until it lines up.
When everything is lined up, grease the release pin and put it into its slot. It should now look like this.
Put a new sticker over the lever slot (wipe off any grease first). This keeps water from getting in and freezing the system.
Put a new sticker on the top of the head. Note, I'm using an older cylinder with new stickers, so I have to cut them to fit.
Put the protective plastic cap over the housing and then screw the housing back onto the cylinder head. When it's screwed all the way in, the release pin likely won't be pointing up, so to correct this, uncrew until it is facing up, then screw the nut tight to keep it there.This Snowpulse illustration shows it best. Also note how the big sticker fits on the newer head.
You’re done with the assembly part, now the cylinder is ready to be filled. This can be done at one of four places: some licensed retailers, a paintball shop, a dive shop, or a fire station. You cannot do this at the gas station or on a construction compressor as you need 3000 psi of air! The head comes with a paintball fill fitting, so that’s the easiest route, but beware that paintball shops may not be good about keeping their air dry, which is very important. Dive shops require a paintball to SCUBA adaptor, have dry air, and should be very willing to fill your cylinder in the slow winter months if they are open. Fire stations require a paintball to SCBA adaptor and also have dry air. My experience is limited to fire stations, which is a great option as they should do it for free, every town has one, and they’re often open 24/7. However, it’s a mixed bag as far as how willing they will be to do it. Some stations will even change their minds (Aspen would do it a few years ago, but not anymore), so be sure to be courteous and perhaps consider a donation of some form (although this should be a free community service- you pay taxes right?) to keep them happy. A fifth option could be a ski patrol that uses the packs, but I haven’t tried and am not sure how involved in this they would want to get.
SCBA adaptor attached. Note that the yellow caps are in place. TAKE THESE OFF WHEN YOU FILL, as the caps can be projectiles if you accidentally don't have the trigger pin all the way in. Safety glasses wouldn't be a bad idea.
Looking small in the SCBA tank holder at the fire station.
Whoever you have do it, have them fill the cylinder slowly (to avoid overheating) to 3000psi. Let them know that there is a check valve in the cylinder assembly, so when they unhook the adaptor, the air will stay in (I’ve had some confusion with that one). The cylinder will be hot, so you must cool the cylinder to room temp and then top it off. The reason for this is that gas expands when it is hot, so when the cylinder cools, the volume will drop. The cylinder gauge must read 3000 psi at room temperature. A water or snow bath will work, or just wait a couple hours. If you over fill the cylinder, there is no bleed valve, so to release some air you’ll have to release all of it.
This cylinder was in the green (3000psi) when I filled it, but then it cooled down to this level. It will fill the airbag fine at room temp, but in cold temps out in the backcountry, it might not. Go get it topped off.
My favorite method to cool the cylinder is to fill a Nalgene half full with water. Bring it with you to the filling place and it should get it cool within a few minutes.
Bonus: For air travel, you unfortunately cannot bring a filled cylinder aboard. You must remove the cylinder head from the cylinder body so that security can look inside. Make sure to take these apart before you get to the airport, and keep them that way until you reach your destination. Goes without saying that this should only be done with an empty cylinder! The head should screw off easily by hand, if you encounter resistence, a wrench may be necessary (some early Snowpulses have Loctite on the threads). When you reach your destination, screw the head back on by hand, not too tight and be careful to not cross the threads. You will then have to fill it, so be sure to have an idea on how you will do this wherever you end up. For more on flying, see my airbag overview.
'Look TSA, nothing to see in here, now please, I have powder to shred.' Snowpulse head removed from cylinder. Note the o-ring in the cylinder- be prepared for it to fly off when you unscrew the head.
Also, be sure to check out Snowpulse’s videos.