When working with power tools or on electrical circuits, there are known hazards, especially electrical shock. Anyone can be exposed to these hazards at home or at work, but workers are exposed to more hazards because job sites can be cluttered with tools and materials, fastpaced, and open to the weather. Risk is also higher at work because many jobs involve electric power tools.

As a source of energy, electricity is used without much thought about the hazards it can cause. Because electricity is a familiar part of our lives, it often is not treated with enough caution. As a result, an average of one worker is electrocuted on the job every day of every year.

According to the National Institute for Occupational Safety and Health, the first step for workers to protect themselves is recognizing the many hazards they face on the job. To do this, they must know which situations can place them in danger. Knowing where to look helps to recognize hazards, according to the NIOSH Student Manual on Safety and Health for Electrical Trades.

An electrical hazard exists when a wire is too small a gauge for the current it will carry. Normally, the circuit breaker in a circuit is matched to the wire size. However, in older wiring, branch lines to permanent ceiling light fixtures could be wired with a smaller gauge than the supply cable.

Let’s say a light fixture is replaced with another device that uses more current. The current capacity (ampacity) of the branch wire could be exceeded. When a wire is too small for the current it is supposed to carry, the wire will heat up. The heated wire could cause a fire.

Electrical hazards exist when wires or other electrical parts are exposed. Wires and parts can be exposed if a cover is removed from a wiring or breaker box. Electrical terminals in motors, appliances, and electronic equipment may be exposed. If you contact exposed live electrical parts, you will be shocked. You need to recognize that an exposed electrical component is a hazard.

Three Boundaries

The risk from exposed live parts depends on your distance from the parts. Three “boundaries” are key to protecting yourself from electric shock and one to protect you from arc flashes or blasts. These boundaries are set by the National Fire Protection Association (NFPA 70E).

The limited approach boundary is the closest an unqualified person can approach, unless a qualified person accompanies. A qualified person is someone who has received mandated training on the hazards and on the construction and operation of equipment involved in a task.

The restricted approach boundary is the closest to exposed live parts that a qualified person can go without proper PPE (such as, flame-resistant clothing) and insulated tools. When you’re this close, if you move the wrong way, you or your tools could touch live parts. Same for the next boundary:

The prohibited approach boundary—the most serious—is the distance you must stay from exposed live parts to prevent flashover or arcing in air. Get any closer and it’s like direct contact with a live part.

Improper Grounding Hazards

When an electrical system is not grounded properly, a hazard exists. The most common OSHA electrical violation is improper grounding of equipment and circuitry. The metal parts of an electrical wiring system that we touch (switch plates, ceiling light fixtures, conduit, etc.) should be grounded and at 0 volts.