What is the minimum number of underground workers required for Class B classification?

• A. 50
• B. 25
• C. 150
• D. 75

Answer: (A)

Classifying underground work by how many workers operate there can change the safety and emergency requirements a mine must follow. The switch to Class B happens at the first mid-range workforce level, meaning the operation is large enough to need more formal safety planning and resources than the smallest category, but not so large that it moves into the next higher class. That first threshold marks the minimum for Class B, which is why this option is chosen. The other numbers represent either smaller operations that don’t reach Class B or larger ones that would fall into a higher category, so they don’t meet the minimum for Class B.