Hardly Through The Looking Glass

I'm still looking(perhaps its a secret)but might any one be willing to offer designs, distributors or manufacturers of venting valves for liquid hydrogen pressure containment tanks(or cylinders, whichever you prefer). Preferably ones that don't freeze up eh!. Mabye electricly preheated.... but I'd rather rely on heat transfer techiques that do not use juice or give spark-------ya know! ? Safe you say?; like i present: I enquire on this. What say U. Thank u Sirs