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Course 809: Focus Four - Electrocution Hazards

Safety guides and audits to make your job as a safety professional easier

What is an Electrocution Hazard?

BE SAFE Poster

Definition

Electrocution results when a person is exposed to a lethal amount of electrical energy. An electrical hazard can be defined as a serious workplace hazard that exposes workers to the following:

Therefore, BE SAFE by recognizing, avoiding, and protecting against all of these electrical hazards. These BE SAFE terms are defined as:

B = Burns

A burn is the most common shock-related injury. Burns from electricity are caused by electrical, arc flash, or thermal contact.

E = Electrocution

Electrocution is fatal; it means to kill with electricity. Electrocution results when a human is exposed to a lethal amount of electrical energy.

S = Shock

Shock results when the body becomes part of the electrical circuit; current enters the body at one point and leaves at another. Electrical shock is defined as a reflex response to the passage of electrical current through the body.

A = Arc Flash/Blast

An arc flash is the sudden release of electrical energy through the air when a high-voltage gap exists, and there is a breakdown between conductors. An arc flash gives off thermal radiation (heat) and bright, intense light that can cause burns. Temperatures have been recorded as high as 35,000 °F. High-voltage arcs can also produce considerable pressure waves by rapidly heating the air and creating a blast.

An arc flash can be spontaneous or result from inadvertently bridging electrical contacts with a conducting object. Other causes may include dropped tools or the buildup of conductive dust or corrosion. For more information on arc flash/blast, including best practices in electrical safety, refer to NFPA 70E: Standard for Electrical Safety in the Workplace®

F = Fire

Most electrical distribution fires result from problems with "fixed wiring" such as faulty electrical outlets and old wiring. Problems with cords (such as extension and appliance cords), plugs, receptacles, and switches also cause electrical fires.

E = Explosions

An explosion can occur when electricity ignites an explosive mixture of material in the air.

Examples

Construction worker carrying a ladder.
  • Two workers were moving an aluminum ladder. The ladder came in contact with the overhead power lines and electrocuted one of the workers.
  • When a worker raised the mast on his water well drilling truck, it came into contact with high voltage overhead lines and electrocuted him.
  • The boom of a rotary drilling truck contacted an overhead power line and electrocuted the worker. The victim and another worker had just finished drilling a water well on a residential property. The victim moved the truck away from the well. The victim was standing at the controls, lowering the boom and was thrown several feet away from the truck.
  • A worker fell to the concrete floor while working from an 8’ fiberglass step ladder. He was fatally injured and electrocuted. The worker was changing an energized ballast on a two bulb fluorescent light fixture, located approximately 11' 6" off the ground.
  • A worker was electrocuted while connecting a replacement electrical service box to the electrical service drop to the building.
Skylight a worker fell through

Statistics

Data from the U.S. Bureau of Labor Statistics, (BLS) show electrocution, was the third leading cause of death in construction in 2013, after falls to a lower level, and being struck by objects and equipment.

Electrocutions caused 8.9% of 796 construction worker deaths in 2013. The death rate from electrocutions for the construction industry was 0.84 per 100,000 full-time workers.

The construction occupations with the highest average number of deaths per year due to electrocution were electricians, construction laborers, supervisors/managers, electrical power installers, and repairers.

Contact with Power Lines

Major Hazards:

Overhead and buried power lines are especially hazardous because they carry extremely high voltage.

Overhead and buried power lines are especially hazardous because they carry extremely high voltage. Fatalities are possible as electrocution is the main risk; however, burns and falls from elevations are also hazards that workers are exposed to while working in the vicinity of high voltage power lines. Workers may not realize that cranes are not the only equipment that reaches overhead power lines. Working on a ladder or in a man-basket suspended under or near power lines also poses a risk of electrocution. Please click here to review Toolbox Talk 1.

Important to note: The covering on an overhead power line is primarily for weather protection; therefore, workers need to know if they touch a power line, covered or bare, death is likely.

Voltages of overhead lines range from 120 to 750,000 volts. The most reliable way to know the voltage is to ask the utility company that owns the line.

Practice Identifying Hazards

Try to identify the hazards in the picture below. Then click on the picture to see if you correctly identified the hazards.

Contact with Power Lines (Continued...)

Let’s review an example of an actual accident:

Fall from tilt-up concrete wall
Accident Type: Electrocution
Weather Conditions: Wet Ground
Type of Operation: Remodeling
Size of Work Crew: 2
Union or Non-Union: Non-Union
Competent Safety Monitor on Site: Yes
Safety and Health Program in Effect: No
Was the Worksite Inspected Regularly: Yes
Training and Education Provided: No
Employee Job Title: Carpenter
Age & Sex: 33-male
Time of the Job: 30 Days
Time on Project: 3 Days

Description of Accident

Two employees were installing aluminum siding on a farmhouse when it became necessary to remove a 36- foot high metal pole CB antenna. One employee stood on a metal pick board between two ladders and unfastened the antenna at the top of the house. The other employee, who was standing on the ground, took the antenna to lay it down in the yard. The antenna made electrical contact with a 7200-volt power transmission line 30 feet 10 inches from the house and 23 feet 9 inches above the ground. The employee handling the antenna received a fatal shock and the other employee a minor shock.

Inspection Results

Following its investigation, OSHA issued one citation for two alleged serious violations of its construction standards. Had these standards been adhered to, the fatality might have been prevented.

What would you recommend?

Recommendations

  • Note the presence of power lines and be extremely cautious when working near them. Train employees to recognize and avoid electrical hazards (29CFR 1926.21(b)(2)).
  • Do not permit employees to work near any part of an electrical power circuit that might be contacted in the course of the work. Guard all electrical power circuits against accidental contact by insulating the circuit or de-energizing it or by other effective means that would protect the employee (29CFR 1926.400(C)(1)).

Contact with Power Lines (Continued...)

Let’s review an example of an actual accident:

Fall from tilt-up concrete wall
Accident Type: Electrocution
Weather Conditions: Clear
Type of Operation: Power Line Work
Size of Work Crew: 2
Union or Non-Union: Union
Competent Safety Monitor on Site: Yes
Safety and Health Program in Effect: No
Was the Worksite Inspected Regularly: No
Training and Education Provided: No
Employee Job Title: Lineman
Age & Sex: 44-male
Experience at this Type of Work: 11 Months
Time on Project: 6 Weeks

Description of Accident

A lineman was electrocuted while working on grounded de-energized lines. He was working from a defective basket on an articulated boom aerial lift when the basket contacted energized lines that ran beneath the de-energized lines. The defective basket permitted current to pass through a drain hole cut into the body of the basket, and then through the employee, and to ground via the de-energized line.

Inspection Results

OSHA cited the company for two serious violations and one other-than-serious violation of its construction standards. Had barriers been erected to prevent contact with adjacent energized lines, the electrical shock might have been prevented.

What would you recommend?

Recommendations

  1. Guards or barriers must be erected as necessary to adjacent energized lines (29 CFR 1926.950(d)(1)(v)).
  2. Existing conditions of mechanical equipment, energized lines, equipment, conditions of poles, and an inspection or test will determine the location of the circuit before starting work. (29 CFR 1926.950(b)(1) and .952(a)(1)).
  3. Employees must be instructed on how to recognize and avoid unsafe conditions and on regulations that apply to their work environment (29 CFR 1926.21(b)(2)).

Contact with Power Lines (Continued...)

Let’s review an example of an actual accident:

Fall from tilt-up concrete wall
Accident Type: Electrical Shock
Weather Conditions: Clear/Hot
Type of Operation: Masonry Contractor
Size of Work Crew: 6
Union or Non-Union: Non-Union
Competent Safety Monitor on Site: No
Safety and Health Program in Effect: Inadequate
Was the Worksite Inspected Regularly: Yes
Training and Education Provided: No
Employee Job Title: Cement Finisher
Age & Sex: 34-male
Experience at this Type of Work: 10 Years
Time on Project: 1 Day

Description of Accident

Two employees were spreading concrete as it was being delivered by a concrete pumper truck boom. The truck was parked across the street from the worksite. Overhead power lines ran perpendicular to the boom on the pumper truck. One employee was moving the hose (elephant trunk) to pour the concrete when the boom of the pumper truck came in contact with the overhead rover line carrying 7,620 volts. The employee received a fatal electric shock and fell on the other employee who was assisting him. The second employee received massive electrical shock and burns. ∗Safety training requirement was not being carried out at the time of the accident.

Inspection Results

OSHA cited the employer for not instructing each employee to recognize and avoid unsafe conditions that apply to the work and work areas. The employer was also cited for operating equipment within ten feet of an energized electrical, ungrounded transmission lines rated 50 kV or less and not erecting insulating barriers.

What would you recommend?

Recommendations

  1. Train employees to recognize and avoid unsafe conditions that apply to the work environment [28 CFR 1926.21(b)(2)].
  2. Avoid operating equipment within ten feet of electrical distribution or transmission lines rated 50 kV or less unless the line has been de-energized and visually grounded, or unless insulating barriers – not part of or attached to the equipment -- are provided [29 CFR 1926.600(a)(6)].

Contact with Energized Sources

Major Hazards:

The major hazards regarding contact with energized sources are electrical shock and burns. Electrical shock occurs when the body becomes part of the electric circuit. This occurs when an individual comes in contact with both wires of an electrical circuit (one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor).

Crane working on a bridge.

The severity and effects of an electrical shock depend on a number of factors, such as:

  • the pathway through the body,
  • the amount of current,
  • the length of time of the exposure, and
  • whether the skin is wet or dry.

Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin. On the next page is a table that discusses the effects of electrical shock.

Electrical burns can be arc burns, thermal contact burns, or a combination of burns. Electrical burns are among the most serious burns and require immediate medical attention. They occur when an electric current flows through tissue or bone, generating heat that causes tissue damage. The body cannot dissipate the heat generated by current flowing through the resistance of the tissue. Therefore, burns occur.

Current Reaction
Below 1 milliampere Generally not perceptible
1 milliampere Faint tingle
5 milliampere Slight shock felt; not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries.
6-25 milliamperes Painful shock, loss of muscular control
9-30 milliamperes The freezing current or "let-go" range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.
50 - 150 mlliamperes Extreme pain, respiratory arrest, severe muscular contractions. Death is possible.
1,000 - 4,300 mlliamperes Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely.
10,000 milliamperes Cardiac arrest, severe burns; death likely

(1,000 milliamperes= 1 amp; therefore, 15,000 milliamperes = 15 amp circuit)

To further illustrate how easily a person can receive a fatal shock, consider a voltage that is common to every location in the United States, 120-volts. Under average working conditions where a person is perspiring, they have a resistance of only 1000-ohms from hand-to-hand. Using the simple Ohm’s Law formula (current equals the voltage divided by the resistance), the current flow will be 0.12 amperes or 120 mA.

A fault current may travel through a worker's body, causing electrical burns or death if:

  • the power supply to the electrical equipment is not grounded, or
  • the path has been broken, or
  • if there are live parts or bare wires.

Even when the power system is properly grounded, electrical equipment can instantly change from safe to hazardous because of extreme conditions and rough treatment.

Contact with Energized Sources (Continued...)

Practice Identifying Hazards

Try to identify the hazards in each picture below. Then click on each picture to see if you correctly identified the hazards.

Contact with Energized Sources (Continued...)

Let’s review an example of an actual accident:

Journeyman wiring light light in ceiling
Accident Type: Electrocution
Weather Conditions: Indoor Work
Type of Operation: Installing and trouble-shooting overhead lamps
Size of Work Crew: 15
Competent Safety Monitor on Site: Yes
Safety and Health Program in Effect: Inadequate
Was the Worksite Inspected Regularly: Yes
Training and Education Provided: No
Employee Job Title: Electrician
Age & Sex: 53-male
Experience at this Type of Work: Journeyman
Time on Project: 1 Month

Description of Accident

The employee was attempting to correct an electrical problem involving two non-operational lamps. He proceeded to the area where he thought the problem was. He had not shut off the power at the circuit breaker panel nor had he tested the wires to see if they were live. He was electrocuted when he grabbed the two live wires with his left hand and then fell from the ladder.

Inspection Results

As a result of its investigation, OSHA Issued citations alleging three serious violations. OSHA's construction standards include several requirements that, if they had been followed here, might have prevented this fatality.

What would you recommend?

Recommendations

  • The employer should not allow work to be done on electrical circuits unless an effective lock-out/tagout program is implemented [29 CFR 1926.416(a)(1)].
  • The employer should not allow work to be done on energized electrical circuits or circuits that are not positively de-energized or tagged out [29 CFR 1926.417(a) and.417(c)].

Improper Use of Extension and Flexible Cords

Major Hazards:

The normal wear and tear on extension and flexible cords can loosen or expose wires, creating a hazardous condition. Cords that are not 3-wire type, not designed for hard-usage, or that have been modified, increase the risk of contacting electrical current. With the wide use of power tools on construction sites, flexible extension cords are often necessary.

Because they are exposed, flexible, and unsecured, they are more susceptible to damage than fixed wiring. Hazards are created when cords, cord connectors, receptacles, and cord- and plug-connected equipment are improperly used and maintained.

To reduce hazards, flexible cords must connect to devices and fittings in ways that prevent tension at joints and terminal screws. A flexible cord may be damaged by door or window edges, staples and fastenings, abrasion from adjacent materials, or simply by aging. If the electrical conductors become exposed, there is a danger of shocks, burns, or fire.

When a cord connector is wet, electric current can leak to the equipment grounding conductor, and to anyone who picks up that connector if they provide a path to ground. Such leakage can occur not just on the face of the connector, but at any portion that is wet.

Improper Use of Extension and Flexible Cords (Continued...)

Practice Identifying Hazards

Try to identify the hazards in the pictures below. Then click on the pictures to see if you correctly identified the hazards.

Improper Use of Extension and Flexible Cords (Continued...)

Extension cord with damaged insulation.

Let’s review an example of an actual accident:

A fan connected to a 120-volt electrical system via an extension cord provided ventilation for a worker performing a chipping operation from an aluminum stepladder. The insulation on the extension cord was cut through and exposed bare, energized conductors made contact with the ladder. The ground wire was not attached on the male end of the cord's plug. When the energized conductor made contact with the ladder, the path to ground included the worker's body, resulting in death.

What would you recommend?

Recommendation

Though it is possible to properly repair the extension cord, it is always best to replace an extension cord that is damaged. Yes, it may cost a little money to replace the extension cord. However, if you don’t replace the extension cord, and it is not repaired properly a life can be lost and the company will be put at risk.

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. You must answer all of the questions before submitting the quiz.

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1. Electrocution results when a person is exposed to _____.

2. Arc flash temperatures have been recorded as high as _____.

3. Most electrical distribution fires result from problems with _____.

4. An explosion can occur when electricity ignites _____.

5. Overhead and buried power lines are especially hazardous because _____.


Stay safe!

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