Close to 1,000 deaths occur annually nationwide as a result of electrical injuries. The vast majority of these injuries are sustained in the workplace, and with some basic understanding of electrical energy and hazard awareness, employers and employees could prevent them.
First, it is imperative to know electrical injuries can occur in three different ways: thermal burns from contact with an electrical source; cardiac arrest due to the electrical effect on the heart; and muscle, nerve and tissue destruction from a current passing through the body. Thermal burns caused by electrical contact often occur below the skin as current flows through the body. Electricity can travel through various paths including blood vessels, nerves and muscles, skin, tendons, fat, and bones. As a result, the severity of electrical burns is frequently underestimated and inaccurately diagnosed.
Electrical injuries can also cause damage to internal organs and, most critically, the heart. When the path of electricity leads to or near the heart, the severity of the injury is much greater. The heart muscle uses electrical current to contract and circulate blood through the body. Depending on the strength of the current, the heartbeat could be disrupted or stimulated irregularly.
When chambers of the heart contract independently, it is known as ventricular fibrillation. It may be reversed by using an automated external defibrillator (AED). Everyone who has access to an AED should know how to use it, especially when working around electrical energy.
The body also uses its own electrical current to control muscles through the nervous system and nerve endings. If an external electrical current interferes with and interrupts normal nervous control, it can cause a victim to lose control of normal muscle movements. Muscles can then contract violently, breaking bones or even causing the victim to stop breathing. If the current passes through the head, the victim can lose consciousness quickly, resulting in a fall. This can create additional injuries, as well.
Although electric shock is the greatest electrical hazard, additional and more gruesome and painful injuries can occur as a result of arc flash. An arc flash is the light and heat produced from an electric arc supplied with sufficient electrical energy to cause substantial damage, harm, fire or injury.
An arc can generate heat as high as 35,000ºF and a pressure wave blast that can be in excess of 1,000 pounds per square inch. This can result in severe burns, destroying skin and tissue. It can ignite or melt clothing, resulting in further burns. Victims may require skin grafts or amputations. Death is more likely with increased severity of burns, the percent of body area affected and age.
The blast can throw victims great distances, resulting in broken bones, concussions and internal injuries. The blast can cause hearing loss. Sound from a blast has been measured at up to 141 decibels at 2 feet from the source. The intense heat may melt metal electrical components and blast molten droplets considerable distances. These droplets harden rapidly and can lodge in a person’s skin, ignite clothing and cause lung damage.
Recently, an electrical contractor was electrocuted when a de-energized powerline he was coiling on the ground in an oil field contacted an energized overhead powerline. The victim and a co-worker were salvaging a three-phase, 440-volt (V) powerline that was no longer in use. The crew leader, working from an aerial bucket, was releasing the powerline phases from the pole-mounted crossarms, approximately 350 feet away from the workers, by cutting the tie wires.
As the conductors fell to the ground, the worker on the ground coiled and loaded them onto a truck. An energized, single-phase, 7,200V powerline was also present. The pole from which the foreman was releasing the conductors was 22 feet from the energized powerline. A second pole, 150 feet from the foreman and 500 feet from the workers, was closer to the energized line.
As one of the conductors was released, the tension on the remaining conductors caused the second pole to lean into the energized powerline, energizing the salvage powerline. The victim, holding one of the conductors in his hand, was electrocuted. The co-worker, standing next to the victim, received flash burns to his face.
National Institute of Safety and Health (NIOSH) investigators concluded that, to prevent similar occurrences, employers should perform a hazard evaluation at each site before any work is initiated; train employees in the recognition of hazards and methods to control such hazards; develop, implement and enforce a comprehensive written safety program; and comply with labor laws.
No matter who you are, it is important to realize the hazards associated with working with electricity and give it the respect it deserves. Visit www.osha.gov for helpful materials on hazardous energy awareness and avoidance.
Source: NIOSH, “Fatality Assessment and Control Evaluation Program.”