Electrical Safety

Electrically powered equipment can pose a significant hazard to workers, particularly when mishandled or not maintained.  Many electrical devices have high voltage or high power requirements, carrying even more risk.

Electrical Shock Hazards

The major hazards associated with electricity are electrical shock, fire and arc flash.  Electrical shock occurs when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.

The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry.  Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin.

The effect of the shock may range from a slight tingle to severe burns to cardiac arrest.  The chart below shows the general relationship between the degree of injury and amount of current for a 60-cycle hand-to-foot path of one second's duration of shock.  While reading this chart, keep in mind that most electrical circuits can provide, under normal conditions, up to 20,000 milliamperes of current flow.

Current

Reaction

1 Milliampere

Perception level

5 Milliamperes

Slight shock felt; not painful but disturbing

6-30 Milliamperes

Painful shock; “let-go” range

50-150 Milliamperes

Extreme pain, respiratory arrest, severe muscular contraction

1000-4,300 Milliamperes

Ventricular fibrillation

10,000+ Milliamperes

Cardiac arrest, severe burns and probable death

In addition to the electrical shock hazards, sparks from electrical equipment can serve as an ignition source for flammable or explosive vapors.

Arc Flash

A hazardous arc flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. Potential places where this can happen include:

  • Panel boards and switchboards
  • Motor control centers
  • Metal clad switch gear
  • Transformers
  • Motor starters and drive cabinets
  • Fused disconnects
  • Any place that can have equipment failure

In an arc flash incident, an enormous amount of concentrated radiant energy explodes outward from electrical equipment.  The explosion creates pressure waves that can damage a person’s hearing, a high-intensity flash that can damage their eyesight and a superheated ball of gas that can severely burn a worker’s body and melt metal.