Red Seal Welding Practice Exam 2025 - Free Welding Practice Questions and Study Guide

When you hear the popping sound in oxy-fuel welding, it indicates a back fire. This happens when the flame inside the welding torch burns back towards the nozzle, instead of projecting outwards. This can cause the equipment to malfunction, and can be dangerous for the welder if not checked and fixed promptly.

The other options are incorrect because

- Regular operation refers to the normal and expected sounds during welding, which do not include popping.

- Adjustment noise may sound similar to popping, but it is a distinct and much shorter noise. It occurs when adjusting the flame settings, and does not happen continuously.

- Starting up may sometimes result in a popping sound, but it is not the correct answer as starting up refers to turning on the equipment and preparing for welding, not the actual welding process itself.