The world has a lot of different standards for a lot of things, but I have never heard of a place with the default screw thread direction being opposite.
So does each language have a fun mnemonic?
Photo credit: https://3.bp.blogspot.com/-Giy8OrYJTjw/Tfm9Ne5o5hI/AAAAAAAAAB4/c7uBLwjkl9c/s1600/scan0002.jpg
Same with gas regulators that attach to the cylinders, for some reason. Oo and some hub nuts on cars
I’ve heard flammable gas uses reverse (left hand) thread to prevent cross connection. At least for welding gases in NZ; not sure about natural gas.
Acetylene does, gas lines are standard pipe.
Suppose it’s cause natural gas runs at like, 1-3 psi, while a fresh tank of acetylene is 5,000?
Least in the US