Departing Washington Dulles last year I saw the screener moving the x-ray belt back and forth on my dry bag...then watched another screener open my bag and say something like "people are crazy!" A second screener joined in on the conversation and said "that can't go". Fortunately I thought to print the airlines policy regarding pfd's and canisters. I asked for a supervisor and after reading the policy she said it was ok. I would check the current online policy and print yourself a copy just incase.