What design feature prevents oxygen and acetylene from mixing inside a welding torch?

• A. Reverse-flow check valves at torch inlets or regulator outlets
• B. Interchangeable gas cartridges
• C. Dual-seal diaphragms in regulators
• D. Color-coded hoses only

Answer: (A)

Preventing backflow of gas so oxygen and acetylene don’t mix inside the torch is the key idea. Gases travel through separate hoses to the torch, but pressure changes or tipping can push gas backward into the other line. A reverse-flow check valve at the torch inlet or at regulator outlets stops that crossflow by allowing flow only toward the torch and closing if pressure would push gas back the other way. This keeps the two gases separate inside the system and prevents dangerous mixtures. Other features don’t provide this cross-gas protection: interchangeable cartridges don’t address flow direction; dual-seal diaphragms help regulate pressure but don’t block reverse flow between different gases; and color coding helps identify gases but doesn’t prevent mixing.