you have to plug one end off. You need a gauge to see how much air you put in. usaully 30lbs is enough. don't keep the air on constantly, air it up and stop the supply then see how much it leaks. Different makes and models of ATA coolers have different specs. take a soapy bottle of water and spray it around the edges of the ATA. Where it's welded to the sides, it usually leaks around there, more than the middle. We check these all the time at work. I can't remember ever having one fixed, we usually install new ones. a small leak will never get better, but it might take along time to get bad enough to change, it's up to you, and your wallet.