Actually, alot of shops i've seen have their air bank set at 3500. They don't have a booster, and after say 10'ish tanks, their air bank drops to 3200'ish and can't go higher than what their air bank is at. So, they start struggling to fill tanks, and it's not the air bank filling them at this point, they are limited by the speed of their compressor. If they have say a 9cu' compressor this could take forever. So they fill to a warm 3200 and when you start your dive you are lucky to have 3k. I'm glad that it's extremely rare that I fill at someone else's shop
