If your avalanche airbag uses compressed air cylinders, you must replace the air cylinder after deploying the airbag or after traveling with an empty cartridge. All you have to do is take the empty air cylinder to a certified refill center and you will get a full one.
Top airbag backpack manufacturers like Backcountry Access and ARVA offer user-refillable canisters that can be filled with compressed air at authorized ski, scuba or paintball shops, and some fire stations. Used ABS cartridges can only be refilled by ABS and exchanged by ABS dealers.