Acetylene is used in gas welding. Despite propane being lessexpensive than acetylene, propane is not used as a fuel in gas welding. It is because of the following reasons: 1. There is far more oxygen being consumed when using propane. 2. Acetylene is lighter than air. If gas leaks out, it will raise higherin the atmosphere. Propane is heavier than air. Any propaneleak in an enclosed area will sink and become concentratedat the deck level, accumulate and sometimes avoid detection. Hence, acetylene is generally used as fuel in gas welding.