I continue to be amazed at the lassez-faire attitude towards filling of bottles by unapproved methods, particularly as those doing it should know better.
Suffice to say that the risks far outweigh any benefits, and if it does go badly wrong, you will end up paying for it in one way or another, maybe with your life or serious injury.
Simply not worth the risk. The proper gear is available, why not use it?
In the late 60's we had a demonstration by a Calor Gas representative at a Tonibell depot where I worked. He showed us quite graphically how gas flowed across the floor and how it could ignite from a spark at some distance.
We also had the usual safety talks etc which went in one ear and out of the other for most guys.
We had relief valves for filling the tanks on the icecream vans, when the tank was full the valve would let out gas vapour. One driver left his tank filling and got involved in a conversation with another guy and forgot his tank was filling. When he returned, smoking a cigarette, he thoughtfully threw it away in some scrub alongside the tank, but unfortunately the overflow had been running on his tank for 15 minutes and the scrub was full of gas.
The resulting explosion blew out windows and caused him some burns, but nothing worse as it was relatively open.
Never take risks with inflammables, it just isn't worth risking your life or other's lives.
I'm not being holier than thou, I wouldn't risk my own family or vehicles with these fillers, my tanks are properly installed and maintained.
Peter