Also, if you stick those air-activated warmers in a small zip-lock and seal it, they will deactivate once they have used the oxy in the bag and come back to life again when brought back into the air. I didn't know this until one of our shooters showed me two he had saved and rejuvenated. Not sure how long you can use them before trying to save them or how many times they can be "lazarusized" before they crap out.