I took note of your stance on hot work around p20.. Your link exposed your theory.
Vapor explosions were the most dangerous per your article. Draining the liquid in the system doesn't give you the go ahead to start welding. Vapors will still be present.
Better off just keeping the machine off while tampering.
Fluorine would work even better to keep those cigs lit, we just don't live in an atmosphere with 20% Fluorine.
The most common use of fluorine in its elemental form is in rocket fuels. It has a working similar to oxygen and helps the other matters in rocket fuel to burn.
Florine can react with hydrogen explosively even in dark and at low temperatures. It reacts violently with water to form hydrogen fluoride and releases oxygen that is highly charged with ozone.