Red Seal Welding Practice Exam

What percentage of acetylene in the air makes it explosive?

1. 1%-50%

2. 2.5%-80%

3. 3%-90%

4. 0.5%-75%

The correct answer is: 2.5%-80%

Acetylene becomes explosive when it reaches a high concentration in the air. As such, we can rule out options A and D since they are below the minimum percentage required for explosiveness. Option C is also incorrect as it is above the maximum percentage. Therefore, the correct answer is B which falls within the safe range of 2.5%-80%.