Electrical Hazard Awareness and Minimum Approach Distances
Electricity is a leading cause of fatalities in aerial work. The exam wants distances, not adjectives.
Minimum approach distances
- The whole machine, the platform, the occupants, and any conductive load must stay outside the MAD - not just the operator's body.
- Under OSHA's approach-distance rule for unqualified persons (1910.333(c)(3)), the baseline is 10 ft (3 m) for lines up to 50 kV, plus 0.4 in (1 cm) per kV above 50 kV.
- Clearance escalates with voltage: 1926.1408 Table A gives 15 ft for 50–200 kV, 20 ft for 200–350 kV, 25 ft for 350–500 kV, 35 ft for 500–750 kV, and 45 ft for 750–1000 kV. Many employers apply the same ladder to lifts.
- Qualified line-clearance workers use the MAD tables in 1910.269, which require specific training, cover-up, and insulated tools.
Controls
De-energize and ground with the utility where practicable; otherwise maintain MAD, use a dedicated spotter whose only task is watching the lines, and treat every line as energized. An insulated boom protects only within its rating and only if its dielectric test is current - it is not a licence to touch.
Worked example
A 12.47 kV service drop crosses a parking lot. The baseline 10 ft applies. The platform is 12 ft from the line horizontally, but the boom swings and a gust moves the basket 2 ft - so true working clearance is under 10 ft. Move the lift, or have the utility de-energize.
Traps
- Measuring clearance once, at the start, from the ground.
- Assuming a low-voltage line is safe to crowd (10 ft applies to everything up to 50 kV).
- Forgetting that sag, wind, and re-routing change distances.
- After contact: stay in the platform, warn others away, and call the utility.