Yeah, this is design practice in other industries as well. If you're assembling a process gas delivery system, you'll find that pressure bottles containing fue

Yeah, this is design practice in other industries as well. If you're assembling a process gas delivery system, you'll find that pressure bottles containing fuels (H2, CH4, etc.) have left-hand threads in the delivery valves. Oxidizer bottles (O2,, etc.) have right-hand threads. Associated hardware (regulators, flow limiters, etc.) is also threaded for their intended use. Makes it much harder to accidentally connect an acetylene tank to a cryogenic oxygen delivery line, with resultant catastrophic exothermic disassembly.