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

• A. 10 ft
• B. 15 ft
• C. 20 ft
• D. 25 ft

Answer: (C)

The key idea is keeping a safe distance from overhead power lines when you don’t know the line’s voltage. Electricity can arc across air if the gap is too small, and the risk grows with voltage. When the voltage is unknown, you must assume the worst within that range—up to 350 kV—and maintain a clearance that protects against arcing. That conservative distance is twenty feet, which accounts for potential line sag, crane movement, and the need for reaction time. If you later determine the voltage and it’s lower or higher, you adjust accordingly; higher voltages would require even more clearance, while known lower voltages call for smaller distances.