By Don Winningham, ANAD Safety OfficeMay 17, 2018
ANNISTON ARMY DEPOT, Ala. -- Did you know there is enough electricity in an ordinary Christmas tree light bulb to kill you?
Electricity harms, and can kill, by giving an electric shock.
Electric shock is the passage of electric current through the body. Electric shock can happen without warning and, even if the shock doesn't harm you, reflex action by your muscles may cause falls or sudden moves into other hazards.
The degree of injury from shock depends on three things:
• Amount of current (amperage) that passes through your body
• Length of time you are in contact with the power source
• Path of the current as it passes through the body
Remember, electrical current is directly related to the amount of resistance (ohms) encountered.
We all know water doesn't have much resistance to electricity and, even if you aren't wet, the human body is made up of mostly water.
Even low amperage passing through your body can disrupt the tiny electrical signals in your nerves and cause your heartbeat or breathing to stop.
According to the Bureau of Labor and Statistics' Census of Fatal Occupational Injuries Research File for 2005--2016, electrocution is the fifth leading cause of work-related deaths for 16- to 19-year-olds, after motor vehicle deaths, contact with objects and equipment, workplace homicide and falls.
Electrocution is the cause of seven percent of all workplace deaths among young workers ages 16--19, causing an average of 10 deaths per year.
Coming in contact with an electrical voltage can cause current to flow through the body, resulting in electrical shock and burns.
Serious injury or even death may occur.
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.
The most common shock-related, nonfatal injury is a burn.
Burns caused by electricity may be of three types: electrical burns, arc burns and thermal contact burns.
Electrical burns can result when a person touches electrical wiring or equipment used or maintained improperly.
Typically, such burns occur on the hands. Electrical burns are one of the most serious injuries you can receive.
They need immediate attention.
Additionally, clothing may catch fire and a thermal burn may result from the heat of the fire.
Arc blasts or flashes cause the most fatal shock-related injuries.
Arc-blasts and flashes occur when powerful, high-amperage currents arc through the air. Arcing is the luminous electrical discharge when high voltages cross a gap between conductors and current travels through the air.
This situation is often caused by equipment failure due to abuse or fatigue.
Temperatures as high as 35,000 degrees Fahrenheit have been reached in arc-blasts.
A common example of arcing is the flash you sometimes see when you turn a light switch on or off. This is not dangerous, because of the low voltage.
There are three primary hazards associated with an arc-blast/flash:
1. Arcing gives off thermal radiation (heat) and intense light, which can cause burns. Several factors affect the degree of injury, including skin color, area of skin exposed and type of clothing worn. Proper clothing, work distances and overcurrent protection can reduce the risk of such a burn.
2. A high-voltage arc can produce a considerable pressure wave blast. A person two feet away from a 25,000-amp arc feels a force of about 480 pounds on the front of the body. In addition, such an explosion can cause serious ear damage and memory loss, due to concussion. Sometimes, the pressure wave throws the victim away from the arc-blast. While this may reduce further exposure to the thermal energy, serious physical injury may result. The pressure wave can propel large objects over great distances. In some cases, the pressure wave has enough force to snap the heads off steel bolts and knock over walls.
3. A high-voltage arc can also cause many of the copper and aluminum components in electrical equipment to melt. These droplets of molten metal can be blasted great distances by the pressure wave. Although these droplets harden rapidly, they can still be hot enough to cause serious burns or cause ordinary clothing to catch fire, even if you are 10 feet or more away.
There are three boundaries which 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 three boundaries are:
The limited approach boundary is the closest an unqualified person can approach, unless a qualified person accompanies you. 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 personal protective equipment, 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.
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.
According to NFPA 70E Article 110.2(D)(1)(e), page 15, General Requirements for Electrical Safety-Related Work Practices, the specifications between a qualified and an unqualified person are defined. This is to specify the requirements of electrical safety training, retraining and certification.
The standard defines a qualified person as one who "shall be trained and knowledgeable of the construction and operation of equipment or a specific work method and be trained to Recognize and avoid the electrical hazards that might be present with respect to that equipment or work method."
An unqualified person is said to be "trained in, and familiar with, any electrical safety-related practices necessary for their safety."
Here at Anniston Army Depot, the only personnel who are recognized as qualified in accordance with the NFPA definition and requirements are in the Directorate of Public Works. These individuals are the only depot employees designated as a "Qualified Electrical Workers."