Sure there is.
I have them sign a 32 page waiver initialled on every page, absolving me, my relatives, freinds, known associates, high school classmates, both ex-wives, Bob (my goldfish) and the counter person at Starbucks who provides my coffee fix of everything up to and including criminal negligence. The waiver must be copied and signed in triplicate, witnessed by two other unrelated people, notorized and then filed with the clerk of courts office for every tank that is filled. I also require my own visual inspection prior to each fill and I have a separate waiver process for nitrox fills. There is then a background check and a mandatory 5 day "cooling off" period to ensure they do not use the gas in a fit of passionate rage. The VIP's are admittedly inconvenient, but the back ground check is good for a whole year.
I don't worry too much about getting sued now, but I have noticed business has been pretty slow since I adopted the new policy.