Not to be the crabby one, but cracking the valve on the tank --opening it slightly for just a moment, to allow a burst of gas to blow out any dust/dirt/crud-- is simply not that dangerous. Don't fling the valve open wide, of course, and let it get away from you, but that's not what "cracking the valve" is: open it just a crack, enough to hear it hiss. If it's O2 or a flammable gas, don't do it near an open source of flame, but for inert gas, it's no big whoop.
I've even been blasted by the stream with no more effect than to make me jump from surprise, and as anyone who has played with a sandblaster can tell you, any particle so small as might get stuck in the threads of a valve would do absolutely nothing: it doesn't have the mass to do more than sting.