Recognizing Electrical Hazards on Site

Electrical contact hurts people in four main ways, and often more than one at once:

• Electrocution — current passing through the body stops the heart. This is the fatal one.
• Electric shock — a jolt that can throw you, freeze your muscles, or knock you off a ladder.
• Burns — the most common electrical injury, from current through the body, from arc flash, or from touching hot equipment.
• Falls and other injuries — a shock high up sends workers off scaffolds, ladders, and roofs.

That last one matters on construction sites. A shock that wouldn't kill you at ground level can put you over a guardrail. Treat every electrical hazard as a fall hazard too when you're up high.

It's the amount of current — the amps — flowing through your body that does the damage, and it takes surprisingly little. Some reference points:

• About 1 milliamp (mA) — you can just feel it.
• 10 mA — muscles clamp and you may not be able to let go of the source.
• 100 mA or so, across the heart — enough to send it into fibrillation and kill you.

OSHA treats 50 volts and above as a shock hazard, but even ordinary 120-volt jobsite power kills people every year. What decides how much current flows is how good a path you make: wet skin, sweat, standing water, and metal all drop your resistance and drive the current up. Don't judge a hazard by how 'low' the voltage sounds.

Most jobsite shocks trace back to a short list of conditions. Watch for:

• Damaged or worn cords and tools — cuts, cracks, exposed conductors, missing ground pins.
• Missing or defeated grounding, and no GFCI protection on temporary power.
• Overhead and buried power lines near cranes, ladders, scaffolds, and digging.
• Wet conditions — rain, puddles, and washdown that turn everything into a conductor.
• Overloaded circuits, daisy-chained cords, and makeshift 'temporary' wiring that never gets fixed.

If you can name the hazard, you can stop before it gets you. When a tool, cord, or setup looks wrong, take it out of service and tell your supervisor — no production goal is worth a contact.