Originally posted December 30, 2013 by Chris Kilbourne on http://safetydailyadvisor.blr.com
What causes electrical shocks?
Electricity travels in closed circuits, normally through a conductor. But sometimes a person’s body—an efficient conductor of electricity—mistakenly becomes part of the electric circuit. This can cause an electrical shock. Shocks occur when a person’s body completes the current path with:
- Both wires of an electric circuit
- One wire of an energized circuit and the ground
- A metal part that accidentally becomes energized
- Another “conductor” that is carrying a current
When a worker receives a shock on the job, electricity flows between parts of the body or through the body to a ground or the earth.
What effect do shocks have on the body?
An electric shock can result in anything from a slight tingling sensation to immediate cardiac arrest. The severity depends on:
- Amount of current flowing through the body
- Current’s path through the body
- Length of time the body remains in the circuit
- Current’s frequency
How can workers tell if a shock is serious?
A severe shock can cause considerably more damage than meets the eye. A victim may suffer internal hemorrhages and destruction of tissues, nerves, and muscles that aren’t readily visible. Renal damage also can occur. If an employee receives a shock, he or she should seek emergency medical help immediately.
What kind of burns can a shock cause?
Burns are the most common shock-related injury. An electrical accident can result in an electrical burn, arc burn, thermal contact burn, or a combination of burns.
- Electrical burns are among the most serious burns and require immediate medical attention. They occur when electric current flows through tissues or bone, generating heat that causes tissue damage.
- Arc or flash burns result from high temperatures caused by an electric arc or explosion near the body. These burns should be treated promptly.
- Thermal contact burns are caused when the skin touches hot surfaces of overheated electric conductors, conduits, or other energized equipment. Thermal burns also can be caused when clothing catches on fire, as may occur when an electric arc is produced.
In addition to shock and burn hazards, electricity poses other dangers. For example, arcs that result from short circuits can cause injury or start a fire. Extremely high-energy arcs can damage equipment, causing fragmented metal to fly in all directions. Even low-energy arcs can cause violent explosions in atmospheres that contain flammable gases, vapors, or combustible dusts.
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 imply low hazard.
In addition to muscle contractions that cause “freezing,” electrical shocks also can cause involuntary muscle reactions. These reactions can result in a wide range of other injuries from collisions or falls, including bruises, bone fractures, and even death.
What should employees do if a co-worker “freezes” to a live electrical contact?
If a co-worker is “frozen” to a live electrical contact, employees should shut off the current immediately. If this is not possible, they can 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 employees should remember to protect themselves as well from electrocution or shock.
How is static electricity hazardous?
Static electricity also can cause a shock, though in a different way and generally not as potentially severe as the type of shock described previously. Static electricity can build up on the surface of an object and, under the right conditions, can discharge to a person, causing a shock. The most familiar example of this is when a person reaches for a door knob or other metal object on a cold, relatively dry day and receives a shock.
However, static electricity also can cause shocks or can just discharge to an object with much more serious consequences, as when friction causes a high level of static electricity to build up at a specific spot on an object. This can happen simply through handling plastic pipes and materials or during normal operation of rubberized drive or machine belts found in many worksites.
In these cases, for example, static electricity can potentially discharge when sufficient amounts of flammable or combustible substances are located nearby and cause an explosion. Grounding or other measures may be necessary to prevent this static electricity buildup and the results.
Avoid Electrical Safety Mistakes and Violations
In October 2013, the preliminary figures for OSHA’s top 10 violations for FY 2013 revealed thousands of violations related to electrical safety. Coming in at number five was “electrical, wiring methods” with 3,452 violations. Common issues involved:
- Problems with flexible cords and cables, boxes, and temporary wiring
- Poor use of extension cords
- Using temporary wiring as permanent wiring
At number eight was “lockout/tagout,” with 3,254 violations ranging from poor or no energy control procedures to inadequate worker training, and incomplete inspections. “Electrical, general” took the number nine spot (2,745 violations) for exposure to electric shock and electrocution.
One of the best ways to improve the overall compliance of your safety program is to take a close look at the electrical safety violations for which OSHA is citing companies, including yours. By taking advantage of these “hard lessons learned” you can use the information to identify gaps in your current program and share what you’ve learned with senior management, facility staff, and your audit team.