Back in my spannering days - which was a while ago - Nitrogen rigs/hoses had right hand threads while oxygen rigs/hoses had left hand threads. I am not sure whether this was a BA convention or a UK convention because I do not think this distinction applied to Europe (at the time anyway).
No, in Germany we have a different system:
Flammable gases (with the exception of acetylene because of it's special dangers), like hydrogen or propane use lefthand male 3/4" threads.
Acetylene uses a clamp connection similar (but not the same) as UK medical cylinders.
Non-flammable gases use righthand 3/4" male threads, but oxygen uses righthand 5/8" male threads, while compressed air (e.g. for scuba equipment) uses righthand 5/8" female threads, so it is impossible unintentionally to e.g. hook up a nitrogen cylinder to an oxygen rig.
(all threads as seen on the cylinder valve).
I also assume that the engineer used a high pressure gauge to fill the tyre, instead of a low pressure one.