Complex sentence: Some gas fittings are left-handed to prevent disastrous misconnections: oxygen fittings are right-handed, but acetylene, propane, and other flammable gases are unmistakably distinguished by left-handed fittings.
Split into simpler sentences: Some gas fittings are left-handed to prevent disastrous misconnections. For example, oxygen fittings are right-handed, but acetylene, propane, and other flammable gases use left-handed fittings.