No matter whether you’re working on your own home or are an experienced professional working on a job site, all power tools and electrical systems have the potential to cause harm, sometimes deadly harm.

Electricity can be either “static” or “dynamic.”

Dynamic electricity is the uniform motion of electrons through a conductor; this electron flow is known as electric current. Conductors are materials that allow the movement of electricity through it. Most metals are conductors. Water is a conductor. The human body is a conductor.

Static electricity is an accumulation of electric charge on surfaces as a result of contact and friction with another surface. This contact / friction causes an accumulation of electrons on one surface, and a deficiency of electrons on the other surface.

Electric current cannot exist without an unbroken path to and from the conductor. Electricity will form a “path” or “loop.” When you plug in a device (like a power tool), the electricity takes the easiest path from the plug / power source to the tool and back to the power source. This action is also known as creating or completing an electrical circuit.

The amount of current needed to light an ordinary 60-watt lightbulb is five times what can kill a person.

See also our short video “Everyday Electrical,” and information geared specifically to the construction trades.

What kinds of injuries result from electrical currents?

People are injured when they become part of the electrical circuit. Humans are more conductive than the earth, the ground we stand on, which means if there is no other easy path then electricity will try to flow through our bodies.

What kinds of injuries result from electrical currents?

There are four main types of injuries:

1. Electrocution (fatal)
2. Electric shock
3. Burn
4. Fall

These injuries can happen due to either direct or indirect connection to live electricity:

A person has direct contact with exposed energized conductors (frayed cord, active power socket, etc.) or circuit parts. The human here directly provides a new closed circuit for the electricity to flow through.

A person has indirect contact when the electricity arcs – or jumps – from an exposed energized conductor or circuit part (e.g., overhead power lines) through a gas (such as air) to a person who is grounded.

This provides an alternative route to the ground for the electrical current (jumping).

Whether from direct or indirect sources, when electrical current travels through a human body it can interfere with the normal electrical signals between the brain and muscles (e.g., heart may stop beating properly, breathing may stop, or muscles can spasm). Potential injuries include:

Thermal burns from direct contact with an electric arc or flame burns from materials that catch on fire. Contact burns can burn internal tissues while leaving only very small injuries visible on the outside of the skin.

Thermal burns from the heat radiated from an electric arc flash. Again, the internal damage may only leave small injuries visible on the skin.

Eye damage from ultraviolet (UV) and infrared (IR) light emitted from the arc flash.

Internal injuries from the pressure wave released from an arc flash. This wave can cause physical injuries, collapse your lungs, or create noise that can damage your hearing.

Falls caused by muscle contractions or a startle reaction that result from an electric shock.

Muscle contractions and sudden muscle / body jerks can cause a person to fall from a ladder, scaffold or aerial bucket. Beyond the possible electrical burn, the fall itself can cause serious or fatal injuries. These can also lead to severe cuts and puncture wounds if the shock occurs while you’re handling power tools with sharp blades or pneumatic pressure (i.e., nail guns, chainsaws, circular saws, etc.).

Safety tips for working with power tools

• Switch all tools to OFF before connecting them to a power supply.
• Do not bypass the on/off switch and operate the tool by connecting and disconnecting the power cord.
• Disconnect and lock out the power supply before completing any maintenance work tasks or adjustments.
• Ensure tools are properly grounded or double-insulated. The grounded equipment must have an approved 3-wire cord with a 3-prong plug. This plug should be plugged into a properly grounded outlet.
• Test all tools for effective grounding with a continuity tester or a ground fault circuit interrupter (GFCI) before use.
• Do not use electrical equipment in wet conditions or damp locations unless the equipment is connected to a GFCI.
• Do not clean tools with flammable or toxic solvents.
• Do not operate tools in an area containing explosive vapors or gases, unless they are intrinsically safe and only if you follow the manufacturer’s guidelines.
• Wear appropriate protective eyewear, gloves and other personal protective equipment.