While most personnel are aware that there is a danger of electrical shock or electrocution in general, many workers are unaware of the potential electrical hazards present in their daily work environment, which makes them more vulnerable to the danger of electrical shock.
The following hazards are the most frequent causes of electrical injuries:
- contact with power lines
- lack of ground-fault protection
- path to ground missing or discontinuous
- equipment not used in manner prescribed
- improper use of extension and flexible cords
While some electrical components may not directly pose serious shock or burn hazards, they are often found adjacent to other circuits with potentially lethal levels of energy.
Even a minor shock can cause a worker to accidentally contact or drop a tool into a live circuit. Involuntary reaction to a shock may also result in bruises, bone fractures, and even death from collisions or falls.
Electric shock occurs when the body becomes a part of an electric circuit. The electrical current must enter the body at one point and leave at another.
Electric shock normally occurs in 1 of 3 ways. Individuals, while in contact with the ground, must come in contact with:
- both wires of an energized circuit, or
- one wire of an energized circuit and the ground, or
- a metallic part that has become "hot" by contact with an energized conductor
The metal parts of electric tools and machines may become energized if there is a break in the insulation of the tool or machine wiring. A worker using these tools and machines is made less vulnerable to electric shock when there is a low-resistance path from the metallic case of the tool or machine to the ground.
This is done using an equipment grounding conductor, a low-resistance wire that causes the unwanted current to pass directly to the ground, thereby greatly reducing the amount of current passing through the body of the person in contact with the tool or machine. If you come into contact with an improperly grounded electrical device, you will be shocked.
Current – the movement of electrical charge
Electrical Shock – a sudden discharge of electricity through a part of the body that may result in injury
Electrocution – death by electric shock
Resistance – opposition to current flow
Voltage – a measure of electrical force
Conductors – substances that have little resistance to electricity
Insulators – substances that have high resistance to electricity
Grounding – a conductive connection to the earth which acts as a protective measure
Pure water is a poor conductor, but small amounts of impurities in water like salt, acid, solvents, or other materials can turn water into a conductor. Dry wood, for example, generally slows or stops the flow of electricity. But when saturated with water, wood turns into a conductor. The same is true of human skin. Dry skin has a fairly high resistance to electric current. But when skin is moist or wet, it acts as a conductor. Anyone working with electricity in a damp or wet environment needs to exercise extra caution to prevent electrical hazards.
An electric shock is received when electrical current passes through the body and can result in anything from a slight tingling sensation to immediate cardiac arrest. The severity depends on the following:
- the amount of current flowing through the body
- the current’s path through the body
- the length of time the body remains in the circuit
- the current’s frequency
A severe shock can cause considerably more damage than meets the eye. A victim may suffer internal hemorrhages, renal damage and destruction of tissues, nerves, and muscles that aren’t readily visible. A small current that passes through the trunk of the body (heart and lungs) can cause severe injury or electrocution. Burns are the most common shock-related injury. If you or a co-worker receives a shock, seek emergency medical help immediately.
Why do people sometimes “freeze” when they are shocked?
When a person receives an electrical shock, sometimes the electrical stimulation causes the muscles to contract. This “freezing” effect makes the person unable to pull free of the circuit. It is extremely dangerous because it increases the length of exposure to electricity and because the current causes blisters, which reduce the body’s resistance and increases the current.
The longer the exposure, the greater the risk of serious injury. Longer exposures at even relatively low voltages can be just as dangerous as short exposures at higher voltages. Low voltage does not mean low hazard.
If a person is “frozen” to a live electrical contact, shut off the current immediately. If this is not possible, use boards, poles, or sticks made of wood or any other nonconducting materials and safely push or pull the person away from the contact.
It’s important to act quickly but remember to protect yourself as well from electrocution or shock.