OSHA requires clearance of ______ when voltage is unknown over 350 kV.

• A. 40 ft
• B. 50 ft
• C. 60 ft
• D. 70 ft

Answer: (B)

When voltage is unknown, you must treat the situation with the highest level of precaution and keep a conservative distance from all exposed energized parts. Air can conduct electricity if the voltage is high enough, so the safer approach is to apply the larger clearance associated with voltages over 350 kV. That conservative buffer—fifty feet—helps prevent arcing or contact if the actual voltage turns out to be higher than anticipated. In crane and heavy equipment work, this means establishing and maintaining a clear exclusion zone of fifty feet from any exposed energized parts until voltage is verified and the area is declared safe.