Question 129General Subjects - QMED

The correct answer is A) Open the acetylene valve very slightly to light-off and then open and adjust the oxygen valve. This is the correct procedure because acetylene is the fuel gas and requires less oxygen to ignite compared to the oxygen gas. By opening the acetylene valve first and just slightly, you can safely ignite the torch without the risk of a flashback or explosion that could occur if you were to open the oxygen valve first. Once the acetylene is lit, you can then open and adjust the oxygen valve to the proper mixture for the welding or cutting application. The other options are incorrect because they either open the oxygen valve first (B and D), which is unsafe, or they open both gases at the same time (C), which also poses a risk of a flashback or explosion.