Student Manual

Workplace

Safety and Health
Ordering Information

To receive documents or other information about occupational safety and

health topics, contact the National Institute for Occupational Safety and

Health (NIOSH) at

NIOSH—Publications Dissemination

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Telephone: 1–800–35–NIOSH (1–800–356–4674)

Fax number: 513–533–8573

E-mail: pubstaft@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh

This document is in the public domain and may

be freely copied or reprinted.

Disclaimer: Mention of any company or product

does not constitute endorsement by NIOSH.

DHHS (NIOSH) Publication No. 2002-123
Student Manual

January 2002
ii

Acknowledgments

This document was prepared by Thaddeus W. Fowler, Ed.D., and Karen K.

Miles, Ph.D., Education and Information Division (EID) of the National

Institute for Occupational Safety and Health (NIOSH). Editorial services were

provided by John W. Diether. Pauline Elliott provided layout and design. 

The authors wish to thank John Palassis and Diana Flaherty (NIOSH), Robert

Nester (formerly of NIOSH), and participating teachers and students for their

contributions to the development of this document. 
Foreword

The National Institute for Occupational Safety and Health (NIOSH) estimates

that 200,000 young workers under the age of 18 suffer work-related injuries in

the United States each year. Young and new workers have a high risk for workrelated injury compared with more experienced workers. Occupational safety 

and health training remains a fundamental element of hazard control in the workplace, and there is great potential to reduce these incidents through pre-employment training. Effective pre-employment training should include realistic environments and hands-on exercises. However, NIOSH recommends that actual

employment in the electrical trades or any of the other construction trades be

delayed until individuals reach the minimum age of 18.

This student manual is part of a safety and health curriculum for secondary and

post-secondary electrical trades courses. The manual is designed to engage the

learner in recognizing, evaluating, and controlling hazards associated with electrical work. It was developed through extensive research with vocational instructors, and we are grateful for their valuable contributions.

Kathleen M. Rest, Ph.D., M.P.A.

Acting Director

National Institute for Occupational Safety and Health

iii

Contents

Page

Section 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Electricity Is Dangerous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

How Is an Electrical Shock Received? . . . . . . . . . . . . . . . . . . . . . 2

Summary of Section 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Section 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Dangers of Electrical Shock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Summary of Section 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Section 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Burns Caused by Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Electrical Fires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Summary of Section 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

First Aid Fact Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Section 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Overview of the Safety Model . . . . . . . . . . . . . . . . . . . . . . . . . . 18

What Must Be Done to Be Safe? . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Summary of Section 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Section 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Safety Model Stage 1—Recognizing Hazards . . . . . . . . . . . . . . . . . 22

How Do You Recognize Hazards? . . . . . . . . . . . . . . . . . . . . . . . . 22

Inadequate wiring hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Exposed electrical parts hazards . . . . . . . . . . . . . . . . . . . . . . . 24

Overhead powerline hazards . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Defective insulation hazards . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Improper grounding hazards . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Overload hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Wet conditions hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Additional hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Summary of Section 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Section 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Safety Model Stage 2—Evaluating Hazards . . . . . . . . . . . . . . . . . . 34

How Do You Evaluate Your Risk? . . . . . . . . . . . . . . . . . . . . . . . . 34

Summary of Section 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

v
vi

Page

Section 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Safety Model Stage 3—Controlling Hazards:

Safe Work Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

How Do You Control Hazards? . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

How Do You Create a Safe Work Environment? . . . . . . . . . . . . . . 36

Lock out and tag out circuits and equipment . . . . . . . . . . . . . . 37

Lock-out/tag-out checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Control inadequate wiring hazards . . . . . . . . . . . . . . . . . . . . . 39

Control hazards of fixed wiring . . . . . . . . . . . . . . . . . . . . . . . . 40

Control hazards of flexible wiring . . . . . . . . . . . . . . . . . . . . . . 40

Use flexible wiring properly . . . . . . . . . . . . . . . . . . . . . . . . 40

Use the right extension cord . . . . . . . . . . . . . . . . . . . . . . . . 42

Control hazards of exposed live electrical parts: isolate

energized components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Control hazards of exposure to live electrical wires:

use proper insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Control hazards of shocking currents . . . . . . . . . . . . . . . . . . . . 46

Ground circuits and equipment . . . . . . . . . . . . . . . . . . . . . . 46

Use GFCI’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Bond components to assure grounding path . . . . . . . . . . . . 49

Control overload current hazards . . . . . . . . . . . . . . . . . . . . . . . 50

Summary of Section 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Section 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Safety Model Stage 3—Controlling Hazards:

Safe Work Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

How Do You Work Safely? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Plan your work and plan for safety . . . . . . . . . . . . . . . . . . . . . 55

Ladder safety fact sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Avoid wet working conditions and other dangers . . . . . . . . . . . 61

Avoid overhead powerlines . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Use proper wiring and connectors . . . . . . . . . . . . . . . . . . . . . . 61

Use and maintain tools properly . . . . . . . . . . . . . . . . . . . . . . . 64

Wear correct PPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

PPE fact sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Summary of Section 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Endnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Photo and Graphics Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Contents (continued)
Section 1

Electricity Is Dangerous

Whenever you work with power tools or on electrical circuits there

is a risk of electrical hazards, especially electrical shock. Anyone

can be exposed to these hazards at home or at work. Workers are

exposed to more hazards because job sites can be cluttered with

tools and materials, fast-paced, and open to the weather. Risk is also

higher at work because many jobs involve electric power tools. 

Electrical trades workers must pay special attention to electrical hazards because they work on electrical circuits. 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! Electrocution is the third leading cause of workrelated deaths among 16- and 17-year-olds, after motor vehicle

deaths and workplace homicide. Electrocution is the cause of

12% of all workplace deaths among young workers.

1

❚ Electrical shock causes injury or

death!

Section 1 Page 1

Electrical Safety

Electrical work can be deadly if not done safely.

Note to the learner—This manual

describes the hazards of electrical work

and basic approaches to working safely.

You will learn skills to help you recognize,

evaluate, and control electrical hazards.

This information will prepare you for additional safety training such as hands-on

exercises and more detailed reviews of

regulations for electrical work.

Your employer, co-workers, and community

will depend on your expertise. Start your

career off right by learning safe practices

and developing good safety habits. Safety

is a very important part of any job. Do it

right from the start.
This manual will present many topics. There are four main types of

electrical injuries: electrocution (death due to electrical shock),

electrical shock, burns, and falls. The dangers of electricity, electrical shock, and the resulting injuries will be discussed. The various

electrical hazards will be described. You will learn about the Safety

Model, an important tool for recognizing, evaluating, and controlling hazards. Important definitions and notes are shown in the

margins. Practices that will help keep you safe and free of injury are

emphasized. To give you an idea of the hazards caused by electricity,

case studies about real-life deaths will be described. 

How Is an Electrical Shock Received?

An electrical shock is received when electrical current passes

through the body. Current will pass through the body in a variety of

situations. Whenever two wires are at different voltages, current will

pass between them if they are connected. Your body can connect the

wires if you touch both of them at the same time. Current will pass

through your body. 

In most household wiring, the black wires and the red wires are at

120 volts. The white wires are at 0 volts because they are connected

to ground. The connection to ground is often through a conducting

ground rod driven into the earth. The connection can also be made

through a buried metal water pipe. If you come in contact with an 

❚ current—the movement of

electrical charge

❚ voltage—a measure of 

electrical force

❚ circuit—a complete path for the flow

of current 

❚ You will receive a shock if you

touch two wires at different

voltages at the same time.

❚ ground—a physical electrical connection to the earth

❚ energized (live, “hot”)—similar

terms meaning that a voltage is 

present that can cause a current, so

there is a possibility of getting

shocked

Page 2 Section 1

ELECTRICITY 

Wires carry current.
energized black wire—and you are also in contact with the neutral white wire—current will pass through your body. You will

receive an electrical shock.

If you are in contact with a live wire or any live component of an

energized electrical device—and also in contact with any

grounded object—you will receive a shock. Plumbing is often

grounded. Metal electrical boxes and conduit are grounded. 

Your risk of receiving a shock is greater if you stand in a puddle of

water. But you don’t even have to be standing in water to be at risk.

Wet clothing, high humidity, and perspiration also increase your

chances of being electrocuted. Of course, there is always a chance of

electrocution, even in dry conditions. 

❚ conductor—material in which an

electrical current moves easily 

❚ neutral—at ground potential (0 volts)

because of a connection to ground

❚ You will receive a shock if 

you touch a live wire and are

grounded at the same time.

❚ When a circuit, electrical 

component, or equipment is 

energized, a potential shock 

hazard is present.

Section 1 Page 3

 IS DANGEROUS

Black and red wires are usually 

energized, and white wires are 

usually neutral.

Metal electrical boxes should be grounded

to prevent shocks.
Page 4 Section 1

You can even receive a shock when you are not in contact with an

electrical ground. Contact with both live wires of a 240-volt cable

will deliver a shock. (This type of shock can occur because one live

wire may be at +120 volts while the other is at -120 volts during an

alternating current cycle—a difference of 240 volts.). You can also

receive a shock from electrical components that are not grounded

properly. Even contact with another person who is receiving an electrical shock may cause you to be shocked.

A30-year-old male electrical technician was helping a company service representative test the voltage-regulating unit on a new rolling mill. While the electrical technician went to get the equipment

service manual, the service representative opened the panel cover of the voltage regulator’s control cabinet in preparation to trace the low-voltage wiring in question (the wiring was not color-coded). The

service representative climbed onto a nearby cabinet in order to view the wires. The technician returned

and began working inside the control cabinet, near exposed energized electrical conductors. The technician tugged at the low-voltage wires while the service representative tried to identify them from above.

Suddenly, the representative heard the victim making a gurgling sound and looked down to see the victim

shaking as though he were being shocked. Cardiopulmonary resuscitation (CPR) was administered to the

victim about 10 minutes later. He was pronounced dead almost 2 hours later as a result of his contact with

an energized electrical conductor.

To prevent an incident like this, employers should take the following steps:

• Establish proper rules and procedures on how to access electrical control cabinets without getting

hurt.

• Make sure all employees know the importance of de-energizing (shutting off) electrical systems before

performing repairs.

• Equip voltage-regulating equipment with color-coded wiring.

• Train workers in CPR.

Amaintenance man rode 12 feet above the floor on a motorized lift to work on a 277-volt light fixture.

He did not turn off the power supply to the lights. He removed the line fuse from the black wire,

which he thought was the “hot” wire. But, because of a mistake in installation, it turned out that the

white wire was the “hot” wire, not the black one. The black wire was neutral. He began to strip the white

wire using a wire stripper in his right hand. Electricity passed from the “hot” white wire to the stripper, then

into his hand and through his body, and then to ground through his left index finger. A co-worker heard a

noise and saw the victim lying face-up on the lift. She immediately summoned another worker, who lowered the platform. CPR was performed, but the maintenance man could not be saved. He was pronounced

dead at the scene.

You can prevent injuries and deaths by remembering the following points:

• If you work on an electrical circuit, test to make sure that the circuit is de-energized (shut off)!

• Never attempt to handle any wires or conductors until you are absolutely positive that their electrical

supply has been shut off.

• Be sure to lock out and tag out circuits so they cannot be re-energized.

• Always assume a conductor is dangerous.

ELECTRICITY 
Summary of Section 1 

You will receive an electrical shock if a part of your body completes

an electrical circuit by •••

touching a live wire and an electrical ground, or

touching a live wire and another wire at a different voltage.

Section 1 Page 5

Always test a circuit to make

sure it is de-energized before

working on it.

 IS DANGEROUS
Section 2

Dangers of Electrical Shock

The severity of injury from electrical shock depends on the amount

of electrical current and the length of time the current passes

through the body. For example, 1/10 of an ampere (amp) of electricity going through the body for just 2 seconds is enough to cause

death. The amount of internal current a person can withstand and

still be able to control the muscles of the arm and hand can be less

than 10 milliamperes (milliamps or mA). Currents above 10 mA

can paralyze or “freeze” muscles. When this “freezing” happens, a

person is no longer able to release a tool, wire, or other object. In

fact, the electrified object may be held even more tightly, resulting

in longer exposure to the shocking current. For this reason, handheld tools that give a shock can be very dangerous. If you can’t let

go of the tool, current continues through your body for a longer

time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). You stop breathing for a period of

time. People have stopped breathing when shocked with currents

from voltages as low as 49 volts. Usually, it takes about 30 mA of

current to cause respiratory paralysis. 

Currents greater than 75 mA cause ventricular fibrillation (very

rapid, ineffective heartbeat). This condition will cause death within a

few minutes unless a special device called a defibrillator is used to

save the victim. Heart paralysis occurs at 4 amps, which means the

heart does not pump at all. Tissue is burned with currents greater

than 5 amps.2

The table shows what usually happens for a range of currents 

(lasting one second) at typical household voltages. Longer exposure

times increase the danger to the shock victim. For example, a current of 100 mA applied for 3 seconds is as dangerous as a current of 

900 mA applied for a fraction of a second (0.03 seconds). The muscle structure of the person also makes a difference. People with less

muscle tissue are typically affected at lower current levels. Even low

voltages can be extremely dangerous because the degree of injury

depends not only on the amount of current but also on the length of

time the body is in contact with the circuit. 

LOW VOLTAGE DOES NOT MEAN LOW HAZARD! 

❚ ampere (amp)—the unit used to

measure current

❚ milliampere (milliamp or mA)—

1/1,000 of an ampere

❚ shocking current—electrical current

that passes through a part of the

body

❚ You will be hurt more if you can’t

let go of a tool giving a shock.

❚ The longer the shock, the greater

the injury.

Page 6 Section 2

DANGERS OF ELE 

Defibrillator in use.
Sometimes high voltages lead to additional injuries. High voltages

can cause violent muscular contractions. You may lose your balance

and fall, which can cause injury or even death if you fall into

machinery that can crush you. High voltages can also cause severe

burns (as seen on pages 9 and 10).

At 600 volts, the current through the body may be as great as 

4 amps, causing damage to internal organs such as the heart. High

voltages also produce burns. In addition, internal blood vessels may

clot. Nerves in the area of the contact point may be damaged.

Muscle contractions may cause bone fractures from either the contractions themselves or from falls.

A severe shock can cause much more damage to the body than is

visible. A person may suffer internal bleeding and destruction of tissues, nerves, and muscles. Sometimes the hidden injuries caused by

electrical shock result in a delayed death. Shock is often only the

beginning of a chain of events. Even if the electrical current is too

small to cause injury, your reaction to the shock may cause you to

fall, resulting in bruises, broken bones, or even death.

The length of time of the shock greatly affects the amount of injury.

If the shock is short in duration, it may only be painful. A longer

❚ High voltages cause additional

injuries!

❚ Higher voltages can cause larger

currents and more severe shocks.

❚ Some injuries from electrical

shock cannot be seen.

Section 2 Page 7

CTRICAL SHOCK

Effects of Electrical Current* on the Body3

Current Reaction

1 milliamp Just a faint tingle.

5 milliamps Slight shock felt. Disturbing, but not painful. Most people can “let go.”

However, strong involuntary movements can cause injuries.

6–25 milliamps (women)† Painful shock. Muscular control is lost. This is the range where “freezing

9–30 milliamps (men) currents” start. It may not be possible to “let go.”

50–150 milliamps Extremely painful shock, respiratory arrest (breathing stops), severe muscle

contractions. Flexor muscles may cause holding on; extensor muscles may

cause intense pushing away. Death is possible.

1,000–4,300 milliamps Ventricular fibrillation (heart pumping action not rhythmic) occurs. Muscles

(1–4.3 amps) contract; nerve damage occurs. Death is likely.

10,000 milliamps Cardiac arrest and severe burns occur. Death is probable.

(10 amps)

15,000 milliamps Lowest overcurrent at which a typical fuse or circuit breaker opens a circuit!

(15 amps)

*Effects are for voltages less than about 600 volts. Higher voltages also cause severe burns.

†Differences in muscle and fat content affect the severity of shock.
shock (lasting a few seconds) could be fatal if the level of current is

high enough to cause the heart to go into ventricular fibrillation.

This is not much current when you realize that a small power drill

uses 30 times as much current as what will kill. At relatively high

currents, death is certain if the shock is long enough. However, if

the shock is short and the heart has not been damaged, a normal

heartbeat may resume if contact with the electrical current is eliminated. (This type of recovery is rare.)

The amount of current

passing through the body

also affects the severity of

an electrical shock. Greater

voltages produce greater

currents. So, there is

greater danger from higher

voltages. Resistance hinders current. The lower the

resistance (or impedance in

AC circuits), the greater the

current will be. Dry skin

may have a resistance of

100,000 ohms or more. Wet

skin may have a resistance

of only 1,000 ohms. Wet

working conditions or broken skin will drastically

reduce resistance. The low

resistance of wet skin

allows current to pass into

the body more easily and

give a greater shock. When more force is applied to the contact point

or when the contact area is larger, the resistance is lower, causing

stronger shocks.

The path of the electrical current through the body affects the severity of the shock. Currents through the heart or nervous system are

most dangerous. If you contact a live wire with your head, your nervous system will be damaged. Contacting a live electrical part with

one hand—while you are grounded at the other side of your body—

will cause electrical current to pass across your chest, possibly injuring your heart and lungs. 

❚ The greater the current, the

greater the shock!

❚ Severity of shock depends on

voltage, amperage, and resistance.

❚ resistance—a material's ability to

decrease or stop electrical current

❚ ohm—unit of measurement for 

electrical resistance 

❚ Lower resistance causes greater

currents.

❚ Currents across the chest are very

dangerous.

Page 8 Section 2

DANGERS OF EL 

Power drills use 30 times as

much current as what will kill.
❚ NEC—National Electrical Code—

a comprehensive listing of 

practices to protect workers and

equipment from electrical hazards

such as fire and electrocution

Section 2 Page 9

ECTRICAL SHOCK

Amale service technician arrived at a customer’s house to perform pre-winter maintenance on an oil

furnace. The customer then left the house and returned 90 minutes later. She noticed the service

truck was still in the driveway. After 2 more hours, the customer entered the crawl space with a

flashlight to look for the technician but could not see him. She then called the owner of the company, who

came to the house. He searched the crawl space and found the technician on his stomach, leaning on his

elbows in front of the furnace. The assistant county coroner was called and pronounced the technician

dead at the scene. The victim had electrical burns on his scalp and right elbow.

After the incident, an electrician inspected the site. A toggle switch that supposedly controlled electrical

power to the furnace was in the “off” position. The electrician described the wiring as “haphazard and 

confusing.”

Two weeks later, the county electrical inspector performed another inspection. He discovered that incorrect wiring of the toggle switch allowed power to flow to the furnace even when the switch was in the “off”

position. The owner of the company stated that the victim was a very thorough worker. Perhaps the victim

performed more maintenance on the furnace than previous technicians, exposing himself to the electrical

hazard.

This death could have been prevented! 

• The victim should have tested the circuit to make sure it was de-energized.

• Employers should provide workers with appropriate equipment and training. Using safety equipment

should be a requirement of the job. In this case, a simple circuit tester may have saved the victim’s life.

• Residential wiring should satisfy the National Electrical Code (NEC). Although the NEC is not retroactive, all homeowners should make sure their systems are safe.

Electrical burn on hand and arm.
DANGERS OF EL 

There have been cases where an arm or leg is severely burned by

high-voltage electrical current to the point of coming off, and the 

victim is not electrocuted. In these cases, the current passes through

only a part of the limb before it goes out of the body and into another

conductor. Therefore, the current does not go through the chest area

and may not cause death, even though the victim is severely disfigured. If the current does go through the chest, the person will almost

surely be electrocuted. A large number of serious electrical injuries

involve current passing from the hands to the feet. Such a path

involves both the heart and lungs. This type of shock is often fatal.

Page 10 Section 2

Arm with third degree burn from 

high-voltage line.
Summary of Section 2

The danger from electrical shock depends on •••

the amount of the shocking current through the body,

the duration of the shocking current through the body, and

the path of the shocking current through the body.

ECTRICAL SHOCK

Section 2 Page 11
Section 3

Burns Caused by Electricity 

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 that is 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 to be given

immediate attention. Additionally,

clothing may catch fire and a

thermal burn may result from the

heat of the fire.

Arc-blasts occur when powerful,

high-amperage currents arc

through the air. Arcing is the

luminous electrical discharge that occurs when high voltages exist

across 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°F have been reached 

in arc-blasts. 

There are three primary hazards associated with an arc-blast.

(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 2 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 

❚ Electrical shocks cause burns.

❚ arc-blast—explosive release of molten

material from equipment caused by

high-amperage arcs

❚ arcing—the luminous electrical discharge (bright, electrical sparking)

through the air that occurs when high

voltages exist across a gap between

conductors 

Page 12 Section 3

BURNS CAUSED 

Contact electrical burns. The

knee on the left was energized,

and the knee on the right was

grounded.
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 off the heads of 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. 

Section 3 Page 13

BY ELECTRICITY

Five technicians were performing preventive maintenance on the electrical system of a railroad maintenance facility. One of the technicians was assigned to clean the lower compartment of an electrical cabinet using cleaning fluid in an aerosol can. But, he began to clean the upper compartment as

well.The upper compartment was filled with live circuitry. When the cleaning spray contacted the live circuitry, a conductive path for the current

was created. The current passed through the stream of fluid, into the

technician’s arm, and across his chest. The current caused a loud

explosion. Co-workers found the victim with his clothes on fire. One

worker put out the fire with an extinguisher, and another pulled the victim away from the compartment with a plastic vacuum cleaner hose.

The paramedics responded in 5 minutes. Although the victim survived the shock, he died 24 hours later of burns.

This death could have been prevented if the following precautions

had been taken:

• Before doing any electrical work, de-energize all circuits and

equipment, perform lock-out/tag-out, and test circuits and

equipment to make sure they are de-energized.

• The company should have trained the workers to perform

their jobs safely.

• Proper personal protective equipment (PPE) should always

be used.

• Never use aerosol spray cans around high-voltage equipment.
14 Section 3

Electrical Fires 

Electricity is one of the most common

causes of fires and thermal burns in

homes and workplaces. Defective or

misused electrical equipment is a

major cause of electrical fires. If

there is a small electrical fire, be

sure to use only a Class C or multipurpose (ABC) fire extinguisher, or

you might make the problem worse.

All fire extinguishers are marked with

letter(s) that tell you the kinds of fires they

can put out. Some extinguishers contain 

symbols, too.

The letters and symbols are explained below (including suggestions on how to remember them). 

A (think: Ashes) = paper, wood, etc.

B (think: Barrel) = flammable liquids

C (think: Circuits) = electrical fires

Here are a couple of fire 

extinguishers at a worksite. 

Can you tell what types of 

fires they will put out?

This extinguisher can only 

be used on Class B and 

Class C fires.

This extinguisher can only

be used on Class A and

Class C fires.

BURNS CAUSED 

Learn how to use fire

extinguishers at work.

However, do not try to put out fires unless you have received

proper training. If you are not trained, the best thing you can

do is evacuate the area and call for help.
Thermal burns may result if an explosion occurs when electricity

ignites an explosive mixture of material in the air. This ignition can

result from the buildup of combustible vapors, gasses, or dusts.

Occupational Safety and Health Administration (OSHA) standards,

the NEC, and other safety standards give precise safety requirements

for the operation of electrical systems and equipment in such dangerous areas. Ignition can also be caused by overheated conductors

or equipment, or by normal arcing at switch contacts or in circuit

breakers. 

Summary of Section 3 

Burns are the most common injury caused by electricity. The three

types of burns are •••

electrical burns,

arc burns, and 

thermal contact burns. 

❚ OSHA—Occupational Safety and

Health Administration—the Federal

agency in the U.S. Department of

Labor that establishes and enforces

workplace safety and health 

regulations

BY ELECTRICITY

Section 3 Page 15
Page 16

Shut offthe electrical current if the victim is still in contact 

with the energized circuit. While you do this, have

someone else call for help. If you cannot get to the

switchgear quickly, pry the victim from the circuit with something that does not 

conduct electricity such as dry wood. Do not touch the victim yourself if he or 

she is still in contact with an electrical circuit! You do not want to be a victim, too! 

Do not leave the victim unless there is absolutely no other option. You should stay

with the victim while Emergency Medical Services (EMS) is contacted. The caller

should come back to you afterwards to verify that the call was made. If the victim is

not breathing, does not have a heartbeat, or is badly injured, quick response by a 

team of emergency medical technicians (EMT’s) or paramedics gives the best chance

for survival.

What Should I Do If a Co-Worker Is

Shocked or Burned by Electricity?

Learn first aid 

First Aid Fact Sheet
Page 17

Once you know that electrical current is no longer flowing through the victim, call out

to the victim to see if he or she is conscious (awake). If the victim is conscious,

tell the victim not to move. It is possible for a shock victim to be seriously injured but

not realize it. Quickly examine the victim for signs of major

bleeding. If there is a lot of bleeding, place a cloth (such

as a handkerchief or bandanna) over the wound and apply

pressure. If the wound is in an arm or leg and keeps bleeding a lot, gently elevate the injured area while keeping

pressure on the wound. Keep the victim warm and talk to

him or her until help arrives. 

If the victim is unconscious, check for signs of breathing. While you do this, move 

the victim as little as possible. If the victim is not breathing, someone trained in 

CPR should begin artificial breathing, then check to see if the victim has a pulse.

Quick action is essential! To be effective, CPR must be performed within 4 minutes 

of the shock.

If you are not trained in CPR or first aid, now is the time to get trained—before you

find yourself in this situation! Ask your instructor or supervisor how you can become

certified in CPR. You also need to know

the location of (1) electricity shut-offs

(“kill switches”), (2) first-aid supplies, and (3) a telephone so you

can find them quickly in an

emergency. 

and CPR now!
Section 4:

Overview of the Safety Model 

What Must Be Done to Be Safe?

Use the three-stage safety model: recognize, evaluate, and control

hazards. To be safe, you must think about your job and plan for 

hazards. To avoid injury or

death, you must understand

and recognize hazards. You

need to evaluate the situation

you are in and assess your

risks. You need to control hazards by creating a safe work

environment, by using safe

work practices, and by reporting hazards to a supervisor or

teacher. 

If you do not recognize, evaluate, and control hazards, you

may be injured or killed by the

electricity itself, electrical

fires, or falls. If you use the

safety model to recognize, 

evaluate, and control hazards,

you are much safer.

(1) Recognize hazards

The first part of the safety model is recognizing the hazards around

you. Only then can you avoid or control the hazards. It is best to 

discuss and plan hazard recognition tasks with your co-workers.

Sometimes we take risks ourselves, but when we are responsible for

others, we are more careful. Sometimes others see hazards that we

overlook. Of course, it is possible to be talked out of our concerns 

❚ Use the safety model to recognize,

evaluate, and control hazards.

❚ Identify electrical hazards.

❚ Don’t listen to reckless,

dangerous people.

Page 18 Section 4

OVERVIEW OF THE 

Report hazards to your supervisor

or teacher.
by someone who is reckless or dangerous. Don’t take a chance.

Careful planning of safety procedures reduces the risk of injury.

Decisions to lock out and tag out circuits and equipment need to be

made during this part of the safety model. Plans for action must be

made now. 

(2) Evaluate hazards

When evaluating hazards, it is best to identify all possible hazards

first, then evaluate the risk of injury from each hazard. Do not

assume the risk is low until you evaluate the hazard. It is dangerous

to overlook hazards. Job sites are especially dangerous because they

are always changing. Many people are working at different tasks.

Job sites are frequently exposed to bad weather. A reasonable place

to work on a bright, sunny day might be very hazardous in the rain.

The risks in your work environment need to be evaluated all the

time. Then, whatever hazards are present need to be controlled.

(3) Control hazards

Once electrical hazards have been recognized and evaluated, they

must be controlled. You control electrical hazards in two main ways:

(1) create a safe work environment and (2) use safe work practices.

Controlling electrical hazards (as well as other hazards) reduces the

risk of injury or death.

OSHA regulations, the NEC, and the National

Electrical Safety Code (NESC) provide a wide

range of safety information. Although these sources

may be difficult to read and understand at first, with

practice they can become very useful tools to help

you recognize unsafe conditions and practices.

Knowledge of OSHA standards is an important part

of training for electrical apprentices. See the

Appendix for a list of relevant standards.

❚ Evaluate your risk.

❚ Take steps to control hazards:

Create a safe workplace.

Work safely.

Section 4 Page 19

SAFETY MODEL

Always lock out and tag out circuits.
Page 20 Section 4 

OVERVIEW OF THE 

Use the safety model to recognize, evaluate, and control workplace hazards like those in 

this picture.
Summary of Section 4 

The three stages of the safety model are •••

Stage 1—Recognize hazards

Stage 2—Evaluate hazards

Stage 3—Control hazards

Section 4 Page 21

SAFETY MODEL
Section 5

Safety Model Stage 1—

Recognizing Hazards

How Do You Recognize Hazards?

The first step toward protecting yourself is recognizing the many

hazards you face on the job. To do this, you must know which situations can place you in danger. Knowing where to look helps you to

recognize hazards.

❑ Inadequate wiring is dangerous.

❑ Exposed electrical parts are dangerous.

❑ Overhead powerlines are dangerous.

❑ Wires with bad insulation can give you a shock.

❑ Electrical systems and tools that are not grounded or double-insulated are dangerous.

❑ Overloaded circuits are dangerous.

❑ Damaged power tools and equipment are electrical hazards.

❑ Using the wrong PPE is dangerous.

❑ Using the wrong tool is dangerous. 

❑ Some on-site chemicals are harmful.

❑ Defective ladders and scaffolding are dangerous. 

❑ Ladders that conduct electricity are dangerous.

❑ Electrical hazards can be made worse if the worker, location, or

equipment is wet.

❚ Workers face many hazards 

on the job.

Page 22 Section 5 

SAFETY MODEL STAGE 1 
Section 5 Page 23

—RECOGNIZING HAZARDS

Worker was electrocuted while removing

energized fish tape.

Fish tape.

An electrician was removing a metal fish tape from a hole at the base of a metal light pole. (A

fish tape is used to pull wire through a conduit run.) The fish tape became energized, electrocuting him. As a result of its inspection, OSHA issued a citation for three serious violations of

the agency’s construction standards.

If the following OSHA requirements had been followed, this death could have been

prevented.

• De-energize all circuits before beginning work.

• Always lock out and tag out de-energized equipment.

• Companies must train workers to recognize and avoid unsafe conditions associated with their work.
Inadequate wiring hazards

An electrical hazard exists when the wire is too small a gauge for the

current it will carry. Normally, the circuit breaker in a circuit is

matched to the wire size. However, in older wiring, branch lines to

permanent ceiling light fixtures could be wired with a smaller gauge

than the supply cable. Let’s say a light fixture is replaced with another

device that uses more current. The current capacity (ampacity) of the

branch wire could be exceeded. When a wire is too small for the current it is supposed to carry, the wire will heat up. The heated wire

could cause a fire.

When you use an extension cord, the size of the wire you are placing into the circuit may be too small for the equipment. The circuit

breaker could be the right size for the circuit but not right for the

smaller-gauge extension cord. A tool plugged into the extension cord

may use more current than the cord can handle without tripping the

circuit breaker. The wire will overheat and could cause a fire.

The kind of metal used as a conductor can cause an electrical

hazard. Special care needs to be taken with aluminum wire.

Since it is more brittle than copper, aluminum wire can crack

and break more easily.

Connections with aluminum

wire can become loose and

oxidize if not made properly,

creating heat or arcing. You

need to recognize that inadequate wiring is a hazard.

Exposed electrical

parts hazards

Electrical hazards exist when

wires or other electrical parts

are exposed. Wires and parts

can be exposed if a cover is

removed from a wiring or

breaker box. The overhead

wires coming into a home

may be exposed. Electrical 

❚ wire gauge—wire size or diameter

(technically, the cross-sectional area)

❚ ampacity—the maximum amount 

of current a wire can carry safely

without overheating 

❚ Overloaded wires get hot!

❚ Incorrect wiring practices can 

cause fires!

❚ If you touch live electrical parts,

you will be shocked.

Page 24 Section 5

SAFETY MODEL STAGE 1 

This hand-held sander has

exposed wires and should not

be used.
terminals in motors, appliances, and electronic equipment may be

exposed. Older equipment may have exposed electrical parts. If you

contact exposed live electrical parts, you will be shocked. You need

to recognize that an exposed electrical component is a hazard.

Overhead powerline hazards

Most people do not realize that overhead powerlines are usually not

insulated. More than half of all electrocutions are caused by direct

worker contact with energized powerlines. Powerline workers must

be especially aware of the dangers of overhead lines. In the past,

80% of all lineman deaths were caused by contacting a live wire

with a bare hand. Due to such incidents, all linemen now wear special rubber gloves that protect them up to 34,500 volts. Today, most

electrocutions involving overhead powerlines are caused by failure

to maintain proper work distances. 

❚ Overhead powerlines kill many

workers!

Section 5 Page 25

—RECOGNIZING HAZARDS

Watch out for exposed electrical wires around 

electronic equipment.

Electrical line workers need special training

and equipment to work safely.
Shocks and electrocutions occur where 

physical barriers are not in place to prevent

contact with the wires. When dump trucks,

cranes, work platforms, or other conductive

materials (such as pipes and ladders) contact

overhead wires, the equipment operator or

other workers can be killed. If you do not

maintain required clearance distances from

powerlines, you can be shocked and killed.

(The minimum distance for voltages up to

50kV is 10 feet. For voltages over 50kV, the

minimum distance is 10 feet plus 4 inches

for every 10 kV over 50kV.) Never store

materials and equipment under or near overhead powerlines. You need to recognize that

overhead powerlines are a hazard.

Defective insulation hazards

Insulation that is defective or inadequate is an electrical 

hazard. Usually, a plastic or rubber covering insulates wires.

Insulation prevents conductors from coming in contact with each

other. Insulation also prevents conductors from coming in contact

with people. 

❚ insulation—material that does not

conduct electricity easily

Page 26 Section 5 

SAFETY MODEL STAGE 1 

Operating a crane near overhead wires is 

very hazardous.

Five workers were constructing a chain-link fence in front of a

house, directly below a 7,200-volt energized powerline. As they

prepared to install 21-foot sections of metal top rail on the

fence, one of the workers picked up a section of rail and held it up

vertically. The rail contacted the 7,200-volt line, and the worker was

electrocuted. Following inspection, OSHA determined that the

employee who was killed had never received any safety training

from his employer and no specific instruction on how to avoid the

hazards associated with overhead powerlines.

In this case, the company failed to obey these regulations:

• Employers must train their workers to recognize and avoid unsafe

conditions on the job.

• Employers must not allow their workers to work near any part of

an electrical circuit UNLESS the circuit is de-energized (shut off)

and grounded, or guarded in such a way that it cannot be contacted.

• Ground-fault protection must be provided at construction sites to

guard against electrical shock.
Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When insulation is damaged, exposed metal

parts may become energized if

a live wire inside touches them.

Electric hand tools that are old,

damaged, or misused may have

damaged insulation inside. If

you touch damaged power tools

or other equipment, you will

receive a shock. You are more

likely to receive a shock if the

tool is not grounded or doubleinsulated. (Double-insulated

tools have two insulation barriers and no exposed metal

parts.) You need to recognize

that defective insulation is a

hazard.

Improper grounding hazards 

When an electrical system is not grounded properly, a hazard exists.

The most common OSHA electrical violation is improper grounding

of equipment and circuitry. The metal parts of an electrical wiring

system that we touch (switch plates, ceiling light fixtures, conduit,

etc.) should be grounded and at 0 volts. If the system is not grounded

properly, these parts may become energized. Metal parts of motors,

appliances, or electronics that are plugged into improperly grounded

circuits may be energized. When a circuit is not grounded properly, a

hazard exists because unwanted voltage cannot be safely eliminated.

If there is no safe path to ground for fault currents, exposed metal

parts in damaged appliances can become energized. 

Extension cords may not provide a continuous path to ground

because of a broken ground wire or plug. If you contact a defective 

❚ If you touch a damaged live power

tool, you will be shocked!

❚ A damaged live power tool that is

not grounded or double-insulated

is very dangerous!

❚ fault current—any current that is not

in its intended path

❚ ground potential—the voltage a

grounded part should have;

0 volts relative to ground 

Section 5 Page 27

—RECOGNIZING HAZARDS

This extension cord is

damaged and should 

not be used.
electrical device that is not grounded (or grounded improperly), you

will be shocked. You need to recognize that an improperly grounded

electrical system is a hazard.

Electrical systems are often grounded to metal water pipes that serve

as a continuous path to ground. If plumbing is used as a path to ground

for fault current, all pipes must be made of conductive material (a type

of metal). Many electrocutions and fires occur because (during renovation or repair) parts of metal plumbing are replaced with plastic pipe,

which does not conduct electricity. In these cases, the path to ground

is interrupted by nonconductive material. 

A ground fault circuit interrupter, or GFCI, is an inexpensive lifesaver. GFCI’s detect any difference in current between the two circuit

wires (the black wires and white wires). This difference in current could happen when electrical

equipment is not working correctly, 

causing leakage current. If leakage 

current (a ground fault) is detected in a

GFCI-protected circuit, the GFCI switches

off the current in the circuit, protecting you

from a dangerous shock. GFCI’s are set at about

5 mA and are designed to protect workers from

electrocution. GFCI’s are able to detect the loss of

current resulting from leakage through a person who is beginning to

be shocked. If this situation occurs, the GFCI switches off the current

in the circuit. GFCI’s are different from circuit breakers because they

detect leakage currents rather than overloads. 

Circuits with missing, damaged, or improperly wired GFCI’s may

allow you to be shocked. You need to recognize that a circuit

improperly protected by a GFCI is a hazard.

Overload hazards

Overloads in an electrical system are

hazardous because they can produce heat

or arcing. Wires and other components

in an electrical system or circuit have a

maximum amount of current they can

carry safely. If too many devices are

plugged into a circuit, the electrical current will heat the wires to a very high

temperature. If any one tool uses too

much current, the wires will heat up. 

❚ If you touch a defective live 

component that is not grounded,

you will be shocked.

❚ GFCI—ground fault circuit 

interrupter—a device that detects

current leakage from a circuit to

ground and shuts the current off

❚ leakage current—current that does

not return through the intended path

but instead "leaks” to ground 

❚ ground fault—a loss of current from

a circuit to a ground connection

❚ overload—too much current 

in a circuit

❚ An overload can lead to a fire or

electrical shock.

Page 28 Section 5 

SAFETY MODEL STAGE 1 

GFCI receptacle.

Overloads are a major cause 

of fires.
The temperature of the wires can be high enough to cause a fire. If

their insulation melts, arcing may occur. Arcing can cause a fire in

the area where the overload exists, even inside a wall.

In order to prevent too much current in a circuit, a circuit breaker or

fuse is placed in the circuit. If there is too much current in the circuit, the breaker “trips” and opens like a switch. If an overloaded

circuit is equipped with a fuse, an internal part of the fuse melts,

opening the circuit. Both breakers and fuses do the same thing: open

the circuit to shut off the electrical current. 

If the breakers or fuses are too big for the wires they are supposed to

protect, an overload in the circuit will not be detected and the current will not be shut off. Overloading leads to overheating of circuit

components (including wires) and may cause a fire. You need to 

recognize that a circuit with improper overcurrent protection

devices—or one with no overcurrent protection devices at all—

is a hazard.

Overcurrent protection devices are built into the wiring of some

electric motors, tools, and electronic devices. For example, if a tool

draws too much current or if it overheats, the current will be shut off

from within the device itself. Damaged tools can overheat and cause

a fire. You need to recognize that a damaged tool is a hazard. 

Wet conditions hazards

Working in wet conditions is hazardous because you may become an

easy path for electrical current. If you touch a live wire or other

electrical component—and you are well-grounded because you are

standing in even a small puddle of water—you will receive a shock.

❚ circuit breaker—an overcurrent 

protection device that automatically

shuts off the current in a circuit if an

overload occurs 

❚ trip—the automatic opening 

(turning off) of a circuit by a GFCI or

circuit breaker

❚ fuse—an overcurrent protection

device that has an internal part that

melts and shuts off the current in a

circuit if there is an overload

❚ Circuit breakers and fuses that 

are too big for the circuit are 

dangerous.

❚ Circuits without circuit breakers or

fuses are dangerous.

❚ Damaged power tools can cause

overloads.

❚ Wet conditions are dangerous.

Section 5 Page 29

—RECOGNIZING HAZARDS

Damaged equipment can overheat and

cause a fire.
Damaged insulation, equipment, or tools can expose you to live

electrical parts. A damaged tool may not be grounded properly, so

the housing of the tool may be energized, causing you to receive a

shock. Improperly grounded metal switch plates and ceiling lights

are especially hazardous in wet conditions. If you touch a live electrical component with an uninsulated hand tool, you are more likely

to receive a shock when standing in water. 

But remember: you don’t have to be standing in water to be electrocuted. Wet clothing, high humidity, and perspiration also increase

your chances of being electrocuted. You need to recognize that all

wet conditions are hazards.

Additional hazards

In addition to electrical hazards, other types of hazards are present at

job sites. Remember that all of these hazards can be controlled.

❑ There may be chemical hazards. Solvents and other substances

may be poisonous or cause disease.

❑ Frequent overhead work can cause tendinitis (inflammation) in

your shoulders.

❚ An electrical circuit in a damp

place without a GFCI is dangerous!

A GFCI reduces the danger.

❚ There are non-electrical hazards at

job sites, too.

Page 30 Section 5 

SAFETY MODEL STAGE 1 

Overhead work can cause

long-term shoulder pain.
❑ Intensive use of hand tools that involve force or twisting can

cause tendinitis of the hands, wrists, or elbows. Use of hand 

tools can also cause carpal tunnel syndrome, which results when

nerves in the wrist are damaged by swelling tendons or contracting muscles.

❚PPE—personal protective

equipment (eye protection,

hard hat, special clothing,

etc.)

Section 5 Page 31

—RECOGNIZING HAZARDS

Frequent use of some hand tools can cause wrist

problems such as carpal tunnel syndrome.

A22-year-old carpenter’s apprentice was killed when he was struck in the head by a nail

fired from a powder-actuated nail gun (a device that uses a gun powder cartridge to

drive nails into concrete or steel). The nail gun operator fired the gun while attempting

to anchor a plywood concrete form, causing the nail to pass through the hollow form. The nail

traveled 27 feet before striking the victim. The nail gun operator had never received training

on how to use the tool, and none of the employees in the area was wearing PPE.

In another situation, two workers were building a wall while remodeling a house. One of the

workers was killed when he was struck by a nail fired from a powder-actuated nail gun. The

tool operator who fired the nail was trying to attach a piece of plywood to a wooden stud. But

the nail shot though the plywood and stud, striking the victim.

Below are some OSHA regulations that should have been followed.

• Employees using powder- or pressure-actuated tools must be trained to use them safely.

• Employees who operate powder- or pressure-actuated tools must be trained to avoid firing

into easily penetrated materials (like plywood).

• In areas where workers could be exposed to flying nails, appropriate PPE must be used.
❑ Low back pain can result from lifting objects the wrong way or

carrying heavy loads of wire or other material. Back pain can

also occur as a result of injury from poor working surfaces such

as wet or slippery floors. Back pain is common, but it can be disabling and can affect young individuals.

❑ Chips and particles flying from tools can injure your eyes. Wear

eye protection.

❑ Falling objects can hit you. Wear a hard hat.

❑ Sharp tools and power equipment can cause cuts and other

injuries. If you receive a shock, you may react and be hurt 

by a tool.

❑ You can be injured or killed by falling from a ladder or scaffolding. If you receive a shock—even a mild one—you may lose

your balance and fall. Even without being shocked, you could

fall from a ladder or scaffolding.

❑ You expose yourself to hazards when you do not wear PPE.

All of these situations need to be recognized as hazards.

Page 32 Section 5 

SAFETY MODEL STAGE 1 

Lift with your legs, not

your back!

You need to be especially

careful when working on

scaffolding or ladders.
Summary of Section 5 

You need to be able to recognize that electrical shocks, fires, or falls

result from these hazards:

Inadequate wiring

Exposed electrical parts 

Overhead powerlines

Defective insulation

Improper grounding

Overloaded circuits 

Wet conditions

Damaged tools and equipment

Improper PPE

Section 5 Page 33

—RECOGNIZING HAZARDS
Section 6 

Safety Model Stage 2—

Evaluating Hazards

How Do You Evaluate Your Risk?

After you recognize a hazard, your next step is to evaluate your risk

from the hazard. Obviously, exposed wires should be recognized as

a hazard. If the exposed wires are 15 feet off the ground, your risk is

low. However, if you are going to be working on a roof near those

same wires, your risk is high. The risk of shock is greater if you will

be carrying metal conduit that could touch the exposed wires. You

must constantly evaluate your risk.

Combinations of hazards increase your risk. Improper grounding

and a damaged tool greatly increase your risk. Wet conditions combined with other hazards also increase your risk. You will need to

make decisions about the nature of hazards in order to evaluate your

risk and do the right thing to remain safe. 

There are “clues” that electrical hazards exist. For example, if a

GFCI keeps tripping while you are using a power tool, there is a

problem. Don’t keep resetting the GFCI and continue to work. You

must evaluate the “clue” and decide what action should be taken to

control the hazard. There are a number of other conditions that indicate a hazard. 

❑ Tripped circuit breakers and blown fuses show that too much

current is flowing in a circuit. This condition could be due to several factors, such as malfunctioning equipment or a short between

conductors. You need to determine the cause in order to control

the hazard.

❑ An electrical tool, appliance, wire, or connection that feels warm

may indicate too much current in the circuit or equipment. You

need to evaluate the situation and determine your risk.

❑ An extension cord that feels warm may indicate too much current

for the wire size of the cord. You must decide when action needs

to be taken. 

❚ risk—the chance that injury or 

death will occur

❚ Make the right decisions.

❚ short—a low-resistance path

between a live wire and the 

ground, or between wires at 

different voltages (called a fault 

if the current is unintended)

Page 34 Section 6 

SAFETY MODEL STAGE 

Combinations of hazards increase risk.
Any of these conditions, or

“clues,” tells you something

important: there is a risk of fire

and electrical shock. The equipment or tools involved must be

avoided. You will frequently be

caught in situations where you

need to decide if these clues are

present. A maintenance electrician, supervisor, or instructor

needs to be called if there are

signs of overload and you are not

sure of the degree of risk. Ask for

help whenever you are not sure

what to do. By asking for help, you

will protect yourself and others. 

❑ A cable, fuse box, or junction box that feels warm may indicate

too much current in the circuits. 

❑ A burning odor may indicate overheated insulation.

❑ Worn, frayed, or damaged insulation around any wire or other

conductor is an electrical hazard because the conductors could be

exposed. Contact with an exposed wire could cause a shock.

Damaged insulation could cause a short, leading to arcing or a

fire. Inspect all insulation for scrapes and breaks. You need to

evaluate the seriousness of any damage you find and decide how

to deal with the hazard. 

❑ A GFCI that trips indicates there is current leakage from the circuit. First, you must decide the probable cause of the leakage by

recognizing any contributing hazards. Then, you must decide

what action needs to be taken.

Summary of Section 6 

Look for “clues” that hazards are present.

Evaluate the seriousness of hazards.

Decide if you need to take action.

Don’t ignore signs of trouble.

Section 6 Page 35

2—EVALUATING HAZARDS

An 18-year-old male worker, with 15 months of experience at a fast food restaurant, was plugging a toaster into a floor outlet when he received a shock. Since the restaurant was closed for the night, the floorhad been mopped about 10 minutes before the incident. The restaurant manager and another employee

heard the victim scream and investigated. The victim was found with one hand on the plug and the other hand

grasping the metal receptacle box. His face was pressed against the top of the outlet. An employee tried to take

the victim’s pulse but was shocked. The manager could not locate the correct breaker for the circuit. He then

called the emergency squad, returned to the breaker box, and found the correct breaker. By the time the circuit

was opened (turned off), the victim had been exposed to the current for 3 to 8 minutes. The employee checked

the victim’s pulse again and found that it was very rapid.

The manager and the employee left the victim to unlock the front door and place another call for help. Another

employee arrived at the restaurant and found that the victim no longer had a pulse. The employee began

administering CPR, which was continued by the rescue squad for 90 minutes. The victim was dead on arrival

at a local hospital.

Later, two electricians evaluated the circuit and found no serious problems. An investigation showed that the

victim’s hand slipped forward when he was plugging in the toaster. His index finger made contact with an

energized prong in the plug. His other hand was on the metal receptacle box, which was grounded. Current

entered his body through his index finger, flowed across his chest, and exited through the other hand, which

was in contact with the grounded receptacle.

To prevent death or injury, you must recognize hazards and take the right action.

• If the circuit had been equipped with a GFCI, the current would have been shut off before injury occurred.

• The recent mopping increased the risk of electrocution. Never work in wet or damp areas!
Section 7 

Safety Model Stage 3—

Controlling Hazards:

Safe Work Environment

How Do You Control Hazards? 

In order to control hazards, you must first create a safe work environment, then work in a safe manner. Generally, it is best to remove

the hazards altogether and create an environment that is truly safe.

When OSHA regulations and the NEC are followed, safe work environments are created. 

But, you never know when materials or equipment might fail.

Prepare yourself for the unexpected by using safe work practices.

Use as many safeguards as possible. If one fails, another may protect you from injury or death.

How Do You Create a Safe Work Environment?

A safe work environment is created by controlling contact with electrical voltages and the currents they can cause. Electrical currents

need to be controlled so they do not pass through the body. In addition to preventing shocks, a safe work environment reduces the

chance of fires, burns, and falls.

You need to guard against contact with electrical voltages and control electrical currents in order to create a safe work environment.

Make your environment safer by doing the following: 

❑ Treat all conductors—even “de-energized” ones—as if they are

energized until they are locked out and tagged.

❑ Lock out and tag out circuits and machines.

❑ Prevent overloaded wiring by using the right size and 

type of wire.

❑ Prevent exposure to live electrical parts by isolating them.

❑ Prevent exposure to live wires and parts by using insulation.

❑ Prevent shocking currents from electrical systems and tools by

grounding them.

❑ Prevent shocking currents by using GFCI’s.

❑ Prevent too much current in circuits by using overcurrent 

protection devices.

❚ Guard against contact with 

electrical voltages and control

electrical currents to create a 

safe work environment.

Page 36 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 
Lock out and tag out circuits and equipment

Create a safe work environment by locking out and tagging out 

circuits and machines. Before working on a circuit, you must 

turn off the power supply. Once the circuit has been shut off and 

de-energized, lock out the switchgear to the circuit so the power

cannot be turned back on inadvertently. Then, tag out the circuit

with an easy-to-see sign or label that lets everyone know that you are

working on the circuit. If you are working on or near machinery, 

you must lock out and tag out the machinery to prevent startup.

Before you begin work, you must test the circuit to make sure it is 

de-energized.

Section 7 Page 37

HAZARDS: SAFE WORK ENVIRONMENT

At about 1:45 a.m., two journeyman electricians began replacing bulbs and making repairs on light

fixtures in a spray paint booth at an automobile assembly plant. The job required the two 

electricians to climb on top of the booth and work from above. The top of the booth was filled with

pipes and ducts that restricted visibility and movement. Flashlights were required.

The electricians started at opposite ends of the booth. One electrician saw a flash of light, but continued

to work for about 5 minutes, then climbed down for some wire. While cutting the wire, he smelled a burning odor and called to the other electrician. When no one answered, he climbed back on top of the booth.

He found his co-worker in contact with a single-strand wire from one of the lights. Needle-nose wire strippers were stuck in the left side of the victim’s chest. Apparently, he had been stripping insulation from an

improperly grounded 530-volt, single-strand wire when he contacted it with the stripper. In this case, the

electricians knew they were working on energized circuits. The breakers in the booth’s control panel were

not labeled and the lock used for lock-out/tag-out was broken. The surviving electrician stated that locating the means to de-energize a circuit often takes more time than the actual job.

The electrician would be alive today if the following rules had been observed.

• Always shut off circuits—then test to confirm that they are de-energized—before starting a job.

• Switchgear that shuts off a circuit must be clearly labeled and easy to access.

• Lock-out/tag-out materials must always be provided, and lock-out/tag-out procedures must always 

be followed.

Always test a circuit to make sure it is

de-energized before working on it. Lock-out/tag-out saves lives.
Page 38 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 

Lock-Out/Tag-Out Checklist

Lock-out/tag-out is an essential safety procedure

that protects workers from injury while working on

or near electrical circuits and equipment. Lock-out

involves applying a physical lock to the power

source(s) of circuits and equipment after they have

been shut off and de-energized. The source is then

tagged out with an easy-to-read tag that alerts other

workers in the area that a lock has been applied. 

I

n addition to protecting workers from electrical hazards, lock-out/tag-out prevents contact

with operating equipment parts: blades, gears,

shafts, presses, etc. 

Also, lock-out/tag-out prevents the unexpected

release of hazardous gasses, fluids, or solid matter

in areas where workers are present. 

An employee was cutting into a metal pipe using a

blowtorch. Diesel fuel was mistakenly discharged

into the line and was ignited by his torch. The

worker burned to death at the scene.

All valves along the line should have been locked

out, blanked out, and tagged out to prevent the

release of fuel. Blanking is the process of inserting

a metal disk into the space between two pipe

flanges. The disk, or blank, is then bolted in place

to prevent passage of liquids or gasses through

the pipe.

A worker was replacing a V-belt on a dust collector

blower. Before beginning work, he shut down the

unit at the local switch. However, an operator in the

control room restarted the unit using a remote

switch. The worker’s hand was caught between the

pulley and belts of the blower, resulting in cuts and

a fractured finger.

When performing lock-out/tag-out on machinery,

you must always lock out and tag out ALL energy

sources leading to the machinery.

When performing lock-out/tag-out on circuits

and equipment, you can use the checklist below.

✔ Identify all sources of electrical energy for the

equipment or circuits in question.

✔ Disable backup energy sources such as generators and batteries. 

✔ Identify all shut-offs for each energy source.

✔ Notify all personnel that equipment and 

circuitry must be shut off, locked out, and

tagged out. (Simply turning a switch off is

NOT enough.)

✔ Shut off energy sources and lock switchgear

in the OFF position. Each worker should

apply his or her individual lock. Do not give

your key to anyone.

✔ Test equipment and circuitry to make sure

they are de-energized. This must be done by a

qualified person.*

✔ Deplete stored energy by bleeding, blocking,

grounding, etc.

✔ Apply a tag to alert other workers that an

energy source or piece of equipment has been

locked out.

✔ Make sure everyone is safe and accounted for

before equipment and circuits are unlocked

and turned back on. Note that only a qualified

person may determine when it is safe to reenergize circuits.

*OSHA defines a “qualified person” as someone who has

received mandated training on the hazards and on the 

construction and operation of equipment involved in a task.
Control inadequate wiring hazards 

Electrical hazards result from using the wrong size or type of wire.

You must control such hazards to create a safe work environment.

You must choose the right size wire for the amount of current

expected in a circuit. The wire must be able to handle the current

safely. The wire’s insulation must be appropriate for the voltage and

tough enough for the environment. Connections need to be reliable

and protected.

❚ Use the right size and type of

wire.

❚ AWG—American Wire Gauge—

a measure of wire size

Section 7 Page 39

HAZARDS: SAFE WORK ENVIRONMENT

14 AWG 12 AWG 12 AWG 10 AWG 8 AWG 6 AWG 2 AWG 1/0 AWG

(stranded) (solid)

20 amps 25 amps 30 amps 40 amps 55 amps 95 amps 125 amps

Wires come in different sizes. The maximum current each size can conduct safely is shown.
Control hazards of fixed wiring

The wiring methods and size of conductors used in a system depend

on several factors:

❑ Intended use of the circuit system

❑ Building materials

❑ Size and distribution of electrical load

❑ Location of equipment (such as underground burial)

❑ Environmental conditions (such as dampness)

❑ Presence of corrosives

❑ Temperature extremes

Fixed, permanent wiring is better than extension cords, which can be

misused and damaged more easily. NEC requirements for fixed

wiring should always be followed. A variety of materials can be

used in wiring applications, including nonmetallic sheathed cable

(Romex®), armored cable, and metal and plastic conduit. The

choice of wiring material depends on the wiring environment and

the need to support and protect wires.

Aluminum wire and connections should be handled with special

care. Connections made with aluminum wire can loosen due to 

heat expansion and oxidize if they are not made properly. Loose 

or oxidized connections can create heat or arcing. Special clamps

and terminals are necessary to make proper connections using 

aluminum wire. Antioxidant paste can be applied to connections to

prevent oxidation.

Control hazards of flexible wiring

Use flexible wiring properly

Electrical cords supplement fixed wiring by providing the flexibility

required for maintenance, portability, isolation from vibration, and

emergency and temporary power needs.

❚ fixed wiring—the permanent 

wiring installed in homes and 

other buildings

Page 40 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 

Nonmetalic sheathing helps protect

wires from damage.
Flexible wiring can be used for extension cords or power supply

cords. Power supply cords can be removable or permanently

attached to the appliance. 

DO NOT use flexible wiring in situations where frequent inspection

would be difficult, where damage would be likely, or where longterm electrical supply is needed. Flexible cords cannot be used as 

a substitute for the fixed wiring of a structure. Flexible cords must

not be . . .

❑ run through holes in walls, ceilings, or floors;

❑ run through doorways, windows, or similar openings (unless

physically protected);

❑ attached to building surfaces (except with a tension take-up

device within 6 feet of the supply end);

❑ hidden in walls, ceilings, or floors; or 

❑ hidden in conduit or other raceways.

❚ flexible wiring—cables with 

insulated and stranded wire that

bends easily

❚ Don’t use flexible wiring where it

may get damaged.

Section 7 Page 41

HAZARDS: SAFE WORK ENVIRONMENT

A29-year-old male welder was assigned to work on an outdoor concrete platform attached to the

main factory building. He wheeled a portable arc welder onto the platform. Since there was not an

electrical outlet nearby, he used an extension cord to plug in the welder. The male end of the cord

had four prongs, and the female end was spring-loaded. The worker plugged the male end of the cord into

the outlet. He then plugged the portable welder’s power cord into the female end of the extension cord. At

that instant, the metal case around the power cord plug became energized, electrocuting the worker.

An investigation showed that the female end of the extension cord was broken. The spring, cover plate,

and part of the casing were missing from the face of the female connector. Also, the grounding prong on

the welder’s power cord plug was so severely bent that it slipped outside of the connection. Therefore, the

arc welder was not grounded. Normally, it would have been impossible to insert the plug incorrectly. But,

since the cord’s female end was damaged, the “bad” connection was able to occur.

Do not let this happen to you. Use these safe practices:

• Thoroughly inspect all electrical equipment before beginning work.

• Do not use extension cords as a substitute for fixed wiring. In this case, a weatherproof receptacle

should have been installed on the platform.

• Use connectors that are designed to stand up to the abuse of the job. Connectors designed for 

light-duty use should not be used in an industrial environment.
Use the right extension cord

The size of wire in an extension cord must be compatible with the

amount of current the cord will be expected to carry. The amount of

current depends on the equipment plugged into the extension cord.

Current ratings (how much current a device needs to operate) are

often printed on the nameplate. If a power rating is given, it is necessary to divide the power rating in watts by the voltage to find the current rating. For example, a 1,000-watt heater plugged into a 120-volt

circuit will need almost 10 amps of current. Let’s look at another

example: A 1-horsepower electric motor uses electrical energy at the

rate of almost 750 watts, so it will need a minimum of about 7 amps

of current on a 120-volt circuit. But, electric motors need additional

current as they startup or if they stall, requiring up to 200% of the

nameplate current rating. Therefore, the motor would need 14 amps. 

Add to find the total current needed to operate all the appliances

supplied by the cord. Choose a wire size that can handle the total

current.

American Wire Gauge (AWG)

Remember: The larger the gauge number, the 

smaller the wire! 

The length of the extension cord also needs to be considered when

selecting the wire size. Voltage drops over the length of a cord. If a

cord is too long, the voltage drop can be enough to damage equipment. Many electric motors only operate safely in a narrow range of

voltages and will not work properly at voltages different than the

voltage listed on the nameplate. Even though light bulbs operate

(somewhat dimmer) at lowered voltages, do not assume electric

motors will work correctly at less-than-required voltages. Also,

when electric motors start or operate under load, they require more

current. The larger the size of the wire, the longer a cord can be

without causing a voltage drop that could damage tools and 

equipment.

Wire size 

#10 AWG 

#12 AWG 

#14 AWG 

#16 AWG 

Handles up to

30 amps

25 amps 

18 amps 

13 amps 

❚ power—the amount of energy used

in a second, measured in watts

❚ 1 horsepower = 746 watts.

❚ Do not use extension cords that

are too long for the size of wire.

Page 42 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 
The grounding path for extension cords must be kept intact to keep

you safe. A typical extension cord grounding system has four 

components:

❑ a third wire in the cord, called a ground wire;

❑ a three-prong plug with a grounding prong on one

end of the cord;

❑ a three-wire, grounding-type receptacle at the other end

of the cord; and

❑ a properly grounded outlet.

Control hazards of exposed live electrical

parts: isolate energized components 

Electrical hazards exist when wires or other electrical parts are

exposed. These hazards need to be controlled to create a safe work

environment. Isolation of energized electrical parts makes them inaccessible unless tools and special effort are used. Isolation can be

accomplished by placing the energized parts at least 8 feet high and

out of reach, or by guarding. Guarding is a type of isolation that uses

various structures—like cabinets, boxes, screens, barriers, covers, and

partitions—to close-off live electrical parts.

❚ Make sure the path to ground is

continuous.

❚ guarding—a covering or barrier that

separates you from live 

electrical parts

Section 7 Page 43

HAZARDS: SAFE WORK ENVIRONMENT

Outlets must be

grounded properly.

This exposed electrical equipment is guarded

by an 8-foot fence. Use covers to prevent

accidental contact with

electrical circuits.
Take the following precautions to prevent injuries from contact with

live parts:

❑ Immediately report exposed live parts to a supervisor or teacher.

As a student, you should never attempt to correct the condition

yourself without supervision.

❑ Provide guards or barriers if live parts cannot be enclosed 

completely.

❑ Use covers, screens, or partitions for guarding that require tools

to remove them.

❑ Replace covers that have been removed from panels, motors, or

fuse boxes.

❑ Even when live parts are elevated to the required height (8 feet),

care should be taken when using objects (like metal rods or

pipes) that can contact these parts. 

❑ Close unused conduit openings in boxes so that foreign objects

(pencils, metal chips, conductive debris, etc.) cannot get inside

and damage the circuit.

Control hazards of exposure to live 

electrical wires: use proper insulation 

Insulation is made of material that does not conduct electricity 

(usually plastic, rubber,or fiber). Insulation covers wires and prevents 

Page 44 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 

A20-year-old male laborer was carrying a 20-foot piece of iron from a welding shop to an outside

storage rack. As he was turning a corner near a bank of electrical transformers, the top end of the

piece of iron struck an uninsulated supply wire at the top of a transformer. Although the transformers were surrounded by a 6-foot fence, they were about 3 feet taller than the fence enclosure. Each

transformer carried 4,160 volts.

When the iron hit the supply wire, the laborer was electrocuted. A forklift operator heard the iron drop to

the ground at about 8:46 a.m. and found the victim 5 minutes later. He was pronounced dead on arrival

at a local hospital.

• According to OSHA, the enclosure around the transformers was too short. The fence should have been

at least 8 feet tall.

• The company in this case did not offer any formal safety training to its workers. All employers should

develop safety and health training programs so their employees know how to recognize and avoid lifethreatening hazards.

This cover cannot be removed 

without special tools.
conductors from coming in contact with each other or any other 

conductor. If conductors are allowed to make contact, a short circuit

is created. In a short circuit, current passes through the shorting

material without passing through a load in the circuit, and the wire

becomes overheated. Insulation keeps wires and other conductors

from touching, which prevents electrical short circuits. Insulation

prevents live wires from touching people and animals, thus protecting them from electrical shock. 

Insulation helps protect wires from physical damage and conditions

in the environment. Insulation is used on almost all wires, except

some ground wires and some high-voltage transmission lines.

Insulation is used internally in tools, switches, plugs, and other electrical and electronic devices.

Special insulation is used on wires and cables that are used in harsh

environments. Wires and cables that are buried in soil must have an

outer covering of insulation that is flame-retardant and resistant to

moisture, fungus, and corrosion. 

In all situations, you must be careful not to damage insulation while

installing it. Do not allow staples or other supports to damage the

insulation. Bends in a cable must have an inside radius of at least 

❚ Make sure insulation is the right

type and in good condition.

Section 7 Page 45

HAZARDS: SAFE WORK ENVIRONMENT

A29-year-old male maintenance worker was found at 3:45 a.m. lying on his back and convulsing.

Beside him were an overturned cart and an electric welding machine, both lying in a pool of water

on the concrete floor. Arcing was visible between the welding machine and the floor. The worker

was transported to the closest hospital, where he was pronounced dead.

An examination of the welding machine showed that there were exposed conductors in the machine’s

cables. There were numerous cuts and scrapes in the cables’ insulation. On other parts of the machine,

insulation was damaged or missing. Also, the machine did not have a ground connection.

Investigators concluded that the maintenance worker was electrocuted when he tried to turn off the welding machine, which was sitting on the cart. The metal frame of the machine had become energized due to

the damaged insulation. When he touched the energized frame, he completed the conducting path to

ground. The current traveled through his body to ground. Since he was probably standing in water, the risk

of a ground fault was even greater.

You must take steps to decrease such hazards in your workplace:

• Ground circuits and equipment.

• Keep all equipment in good operating condition with a preventive maintenance program.

• Never use electrical equipment or work on circuits in wet areas. If you find water or dampness, notify

your supervisor immediately.
5 times the diameter of the cable so that insulation at a bend is not

damaged. Extension cords come with insulation in a variety of types

and colors. The insulation of extension cords is especially important.

Since extension cords often receive rough handling, the insulation

can be damaged. Extension cords might be used in wet places, so

adequate insulation is necessary to prevent shocks. Because extension cords are often used near combustible materials (such as wood

shavings and sawdust) a short in an extension cord could easily

cause arcing and a fire.

Insulation on individual wires is often color-coded. In general, insulated wires used as equipment grounding conductors are either continuous green or green with yellow stripes. The grounded conductors

that complete a circuit are generally covered with continuous white

or gray insulation. The ungrounded conductors, or “hot” wires, may

be any color other than green, white, or gray. They are usually black

or red. 

Conductors and cables must be marked by the manufacturer to show

the following: 

❑ maximum voltage capacity, 

❑ AWG size,

❑ insulation-type letter, and 

❑ the manufacturer’s name or trademark.

Control hazards of shocking currents

Ground circuits and equipment

When an electrical system is not grounded properly, a hazard exists.

This is because the parts of an electrical wiring system that a person

normally touches may be energized, or live, relative to ground. Parts

like switch plates, wiring boxes, conduit, cabinets, and lights need to

be at 0 volts relative to ground. If the system is grounded improperly, these parts may be energized. The metal housings of equipment

plugged into an outlet need to be grounded through the plug.

Page 46 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 

Ground electrical

devices.

Arc-fault circuit

breaker.
Grounding is connecting an electrical system to the earth with a wire.

Excess or stray current travels through this wire to a grounding

device (commonly called a “ground”) deep in the earth. Grounding

prevents unwanted voltage on electrical components. Metal plumbing

is often used as a ground. When plumbing is used as a grounding

conductor, it must also be connected to a grounding device such as a

conductive rod. (Rods used for grounding must be driven at least 

8 feet into the earth.) Sometimes an electrical system will receive a

higher voltage than it is designed to handle. These high voltages may

come from a lightning strike, line surge, or contact with a highervoltage line. Sometimes a defect occurs in a device that allows

exposed metal parts to become energized. Grounding will help 

protect the person working on a system, the system itself, and others

using tools or operating equipment connected to the system. The

extra current produced by the excess voltage travels relatively safely

to the earth. 

Grounding creates a path for currents produced by unintended 

voltages on exposed parts. These currents follow the grounding path,

rather than passing through the body of someone who touches the

energized equipment. However, if a grounding rod takes a direct hit

from a lightning strike and is buried in sandy soil, the rod should be

examined to make sure it will still function properly. The heat from

a lightning strike can cause the sand to turn into glass, which is an

insulator. A grounding rod must be in contact with damp soil to be

effective.

Leakage current occurs when an electrical current escapes from its

intended path. Leakages are sometimes low-current faults that can

occur in all electrical equipment because of dirt, wear, damage, or

moisture. A good grounding system should be able to carry off this

leakage current. A ground fault occurs when current passes through

the housing of an electrical device to ground. Proper grounding protects against ground faults. Ground faults are usually caused by 

misuse of a tool or damage to its insulation. This damage allows a

bare conductor to touch metal parts or the tool housing.

When you ground a tool or electrical system, you create a lowresistance path to the earth (known as a ground connection). When

done properly, this path has sufficient current-carrying capacity to

eliminate voltages that may cause a dangerous shock. 

Grounding does not guarantee that you will not be shocked, injured,

or killed from defective equipment. However, it greatly reduces the

possibility.

Section 7 Page 47

HAZARDS: SAFE WORK ENVIRONMENT

Grounding-type

receptacle.

Grounding rod in

the earth.
Equipment needs to be grounded under any of these circumstances: 

❑ The equipment is within 8 feet vertically and 5 feet horizontally

of the floor or walking surface. 

❑ The equipment is within 8 feet vertically and 5 feet horizontally

of grounded metal objects you could touch. 

❑ The equipment is located in a wet or damp area and is not isolated. 

❑ The equipment is connected to a power supply by cord and plug

and is not double-insulated. 

Use GFCI’s

The use of GFCI’s has lowered the number of electrocutions dramatically. A GFCI is a fast-acting switch that detects any difference in

current between two circuit conductors. If either conductor comes in

contact—either directly or through part of your body—with a

ground (a situation known as a ground fault), the GFCI opens the

circuit in a fraction of a second. If a current as small as 4 to 6 mA

does not pass through both wires properly, but instead leaks to the

ground, the GFCI is tripped. The current is shut off. 

There is a more sensitive kind of GFCI called an isolation GFCI. If

a circuit has an isolation GFCI, the ground fault current passes

through an electronic sensing circuit in the GFCI. The electronic

sensing circuit has enough resistance to limit current to as little as 

2 mA, which is too low to cause a dangerous shock. 

GFCI’s are usually in the form of a duplex receptacle. They are also

available in portable and plug-in designs and as circuit breakers 

that protect an entire branch circuit. GFCI’s can operate on both

two- and three-wire ground systems. For a GFCI to work properly,

the neutral conductor (white wire) must (1) be continuous, (2) have

low resistance, and (3) have sufficient current-carrying capacity. 

GFCI’s help protect you from electrical shock by continuously monitoring the circuit. However, a GFCI does not protect a person from

line-to-line hazards such as touching two “hot” wires (240 volts) at

the same time or touching a “hot” and neutral wire at the same time.

Also be aware that instantaneous currents can be high when a GFCI

is tripped. A shock may still be felt. Your reaction to the shock could

cause injury, perhaps from falling. 

Test GFCI’s regularly by pressing the “test” button. If the circuit

does not turn off, the GFCI is faulty and must be replaced.

❚ GFCI’s have their limitations.

Page 48 Section 7 

SAFETY MODEL STAGE 3—CONTROLLING 

Portable GFCI.
The NEC requires that GFCI’s be used in these high-risk situations:

❑ Electricity is used near water.

❑ The user of electrical equipment is grounded (by touching

grounded material). 

❑ Circuits are providing power to portable tools or outdoor 

receptacles.

❑ Temporary wiring or extension cords are used.

Specifically, GFCI’s must be installed in bathrooms, garages, outdoor areas, crawl spaces, unfinished basements, kitchens, and near

wet bars.

Bond components to assure grounding path

In order to assure a continuous, reliable electrical path to ground, a

bonding jumper wire is used to make sure electrical parts are connected. Some physical connections, like metal conduit coming into a 

❚ Use GFCI’s to help protect people

in damp areas.

❚ bonding—joining electrical parts to

assure a conductive path

Section 7 Page 49

HAZARDS: SAFE WORK ENVIRONMENT

Afemale assistant manager of a swim club was instructed to add a certain chemical to the pool. She

went down into the pump room, barefoot. The room was below ground level, and the floor was 

covered with water. She filled a plastic drum with 35-40 gallons of water, then plugged a mixing

motor into a 120-volt wall outlet and turned on the motor. The motor would be used to mix the water and

the chemical, then the solution would be added to the pool. While adding the chemical to the water in the

drum, she contacted the mixing motor with her left hand. Apparently, the motor had developed a ground

fault. Because of the ground fault, the motor was energized, and she was electrocuted. A co-worker found

the victim slumped over the drum with her face submerged in water. The co-worker tried to move the 

victim but was shocked. The assistant manager was dead on arrival at a local hospital.

An investigation showed that the mixing motor was in poor condition. The grounding pin had been

removed from the male end of the power cord, resulting in a faulty ground. The circuit was equipped with

a GFCI, but it was not installed properly. A properly wired and functioning GFCI could have sensed the

ground fault in the motor and de-energized the circuit.

Take a look at what could have been done to prevent this death.

• The employer should have kept the motor in better condition. Power cords should be inspected 

regularly, and any missing prongs should be replaced.

• All pool-area electrical circuits should be installed by qualified electricians.

• The victim should have worn insulating boots or shoes since she was handling electrical equipment.

• The employer should have followed the law. The NEC requires that all pool-associated motors have a

permanent grounding system. In this case, this regulation was not followed. Also, electrical equipment

is not permitted in areas without proper drainage.

• OSHA requires employers to provide a work environment free of safety and health hazards.

Install bonding jumpers

around nonconductive

material.
box, might not make a good electrical connection because of paint

or possible corrosion. To make a good electrical connection, a bonding jumper needs to be installed. 

A metal cold water pipe that is part of a path to ground may need

bonding jumpers around plastic antivibration devices, plastic water

meters, or sections of plastic pipe. A bonding jumper is made of

conductive material and is tightly connected to metal pipes with

screws or clamps to bypass the plastic and assure a continuous

grounding path. Bonding jumpers are necessary because plastic does

not conduct electricity and would interrupt the path to ground. 

Additionally, interior metal plumbing must be bonded to the ground

for electrical service equipment in order to keep all grounds at the

same potential (0 volts). Even metal air ducts should be bonded to

electrical service equipment.

Control overload current hazards

When a current exceeds the current rating of equipment or wiring, a

hazard exists. The wiring in the circuit, equipment, or tool cannot

handle the current without heating up or even melting. Not only will

the wiring or tool be damaged, but the high temperature of the conductor can also cause a fire. To prevent this from happening, an

overcurrent protection device (circuit breaker or fuse) is used in a

circuit. These devices open a circuit automatically if they detect current in excess of the current rating of equipment or wiring. This

excess current can be caused by an overload, short circuit, or highlevel ground fault.

❚ bonding jumper—the 

conductor used to connect

parts to be bonded

Page 50 Section 7

SAFETY MODEL STAGE 3—CONTROLLING 

Use overcurrent protection devices 

(circuit breakers or fuses) in circuits.
Overcurrent protection devices are designed to protect equipment

and structures from fire. They do not protect you from electrical

shock! Overcurrent protection devices stop the flow of current in a

circuit when the amperage is too high for the circuit. A circuit breaker or fuse will not stop the relatively small amount of current that

can cause injury or death. Death can result from 20 mA (.020 amps)

through the chest (see Section 2). A typical residential circuit breaker or fuse will not shut off the circuit until a current of more than 

20 amps is reached!

But overcurrent protection devices are not allowed in areas where

they could be exposed to physical damage or in hazardous environments. Overcurrent protection devices can heat up and occasionally

arc or spark, which could cause a fire or an explosion in certain

areas. Hazardous environments are places that contain flammable or

explosive materials such as flammable gasses or vapors (Class I

Hazardous Environments), finely pulverized flammable dusts 

(Class II Hazardous Environments), or fibers or metal filings that

can catch fire easily (Class III Hazardous Environments). Hazardous

environments may be found in aircraft hangars, gas stations, storage

plants for flammable liquids, grain silos, and mills where cotton

fibers may be suspended in the air. Special electrical systems are

required in hazardous environments.

If an overcurrent protection device opens a circuit, there may be a

problem along the circuit. (In the case of circuit breakers, frequent

tripping may also indicate that the breaker is defective.) When a circuit breaker trips or a fuse blows, the cause must be found.

A circuit breaker is one kind of overcurrent protection device. It is a

type of automatic switch located in a circuit. A circuit breaker trips

when too much current passes through it. A circuit breaker should

not be used regularly to turn power on or off in a circuit, unless the

breaker is designed for this purpose and marked “SWD” (stands for

“switching device”).

A fuse is another type of overcurrent protection device. A fuse contains a metal conductor that has a relatively low melting point.

When too much current passes through the metal in the fuse, it heats

up within a fraction of a second and melts, opening the circuit. After

an overload is found and corrected, a blown fuse must be replaced

with a new one of appropriate amperage.

❚ Find the cause of an overload.

Section 7 Page 51

HAZARDS: SAFE WORK ENVIRONMENT

Only circuit breakers

marked “SWD” should

be used as switches.
Page 52 Section 7

SAFETY MODEL STAGE 3—CONTROLLING 

Summary of Section 7

Control contact with electrical voltages and control electrical currents to create a safe work environment.

Lock out and tag out circuits and machines.

Prevent overloaded wiring by using the right size and type of wire.

Prevent exposure to live electrical parts by isolating them.

Prevent exposure to live wires and parts by using insulation.

Prevent shocking currents from electrical systems and tools by grounding them.

Prevent shocking currents by using GFCI’s.

Prevent too much current in circuits by using overcurrent protection devices. 
Section 7 Page 53

HAZARDS: SAFE WORK ENVIRONMENT
Section 8 

Safety Model Stage 3—

Controlling Hazards:

Safe Work Practices 

How Do You Work Safely?

A safe work environment is not enough to control all electrical hazards. You must also work safely. Safe work practices help you control your risk of injury or death from workplace hazards. If you are

working on electrical circuits or with electrical tools and equipment,

you need to use safe work practices. 

Before you begin a task, ask yourself: 

❑ What could go wrong? 

❑ Do I have the knowledge, tools, and experience to do this work

safely? 

All workers should be very familiar with the safety procedures 

for their jobs. You must know how to use specific controls that help

keep you safe. You must also use good judgment and common

sense.

Control electrical hazards through safe work practices.

❑ Plan your work and plan for safety.

❑ Avoid wet working conditions and other dangers.

❑ Avoid overhead powerlines. 

❑ Use proper wiring and connectors.

❑ Use and maintain tools properly.

❑ Wear correct PPE. 

Page 54 Section 8 

SAFETY MODEL STAGE 3—CONTROLLING 
Plan your work and plan for safety

Take time to plan your work, by yourself and with others. Safety

planning is an important part of any task. It takes effort to recognize,

evaluate, and control hazards. If you are thinking about your work

tasks or about what others think of you, it is hard to take the time to

plan for safety. But, YOU MUST PLAN. 

Planning with others is especially helpful. It allows you to coordinate your work and take advantage of what others know about identifying and controlling hazards. The following is a list of some

things to think about as you plan.

❑ Work with a “buddy”—Do not work alone. Both of you 

should be trained in CPR. Both of you must know what to do 

in an emergency.

❑ Know how to shut off and de-energize circuits—You must find

where circuit breakers, fuses, and switches are located. Then, the

circuits that you will be working on (even low-voltage circuits)

MUST BE TURNED OFF! Test the circuits before beginning

work to make sure they are completely de-energized.

❚ Plan to be safe.

❚ Don’t work alone.

Section 8 Page 55

HAZARDS: SAFE WORK PRACTICES

A40-year-old male meter technician had just completed a 7-week basic lineman training course. He

worked as a meter technician during normal working hours and as a lineman during unplanned outages. One evening, he was called to repair a residential power outage. By the time he arrived at

the site of the outage, he had already worked 2 hours of overtime and worked 14 straight hours the day

before. At the site, a tree limb had fallen across an overhead powerline. The neutral wire in the line was

severed, and the two energized 120-volt wires were disconnected. The worker removed the tree limb and

climbed up a power pole to reconnect the three wires. He was wearing insulated gloves, a hard hat, and

safety glasses.

He prepared the wires to be connected. While handling the wires, one of the energized wires caught the

cuff of his left glove and pulled the cuff down. The conductor contacted the victim’s forearm near the wrist.

He was electrocuted and fell backwards. He was wearing a climbing belt, which left him hanging upside

down from the pole. Paramedics arrived 5 minutes after the contact.The power company lowered his dead

body 30 minutes later.

Several factors may have contributed to this incident. Below are some ways to eliminate these risk factors.

• Ask for assistance when you are assigned tasks that cannot be safely completed alone. The task

assigned to the victim could not have been done safely by only one person.

• Do not work overtime performing hazardous tasks that are not part of your normal assignments.

• Employees should only be given tasks that they are qualified to perform. All employees below the 

journeyman level should be supervised.
❑ Plan to lock out and tag out circuits and equipment—Make

certain all energy sources are locked out and tagged out before

performing any work on an electrical circuit or electrical device.

Working on energized (“hot”) circuits is one of the most dangerous things any worker could do. If someone turns on a circuit

without warning, you can be shocked, burned, or electrocuted.

The unexpected starting of electrical equipment can cause severe

injury or death. 

Before ANY work is done on a circuit, shut off the circuit, lock

out and tag out the circuit at the distribution panel, then test the

circuit to make sure it is de-energized.

Before ANY equipment inspections or repairs—even on so-called

low-voltage circuits—the current must be turned off at the switch

box, and the switch must be padlocked in the OFF position. At

the same time, the equipment must be securely tagged to warn

everyone that work is being performed. Again, test circuits and

equipment to ensure they are de-energized.

No two locks should be alike. Each key should fit only one lock,

and only one key should be issued to each worker. If more than

one worker is working on a circuit or repairing a piece of equipment, each worker should lock out the switch with his or her own

lock and never permit anyone else to remove it. At all times, you

must be certain that you are not exposing other workers to danger. Workers who perform lock-out/tag-out must be trained and

authorized to repair and maintain electrical equipment. A lockedout switch or feeder panel prevents others from turning on a circuit. The tag informs other workers of your action.

❑ Remove jewelry and metal objects—Remove jewelry and other

metal objects or apparel from your body before beginning work.

These things can cause burns if worn near high currents and can

get caught as you work.

❑ Plan to avoid falls—Injuries can result from falling off scaffolding or ladders. Other workers may also be injured from equipment and debris falling from scaffolding and ladders. 

Page 56 Section 8 

SAFETY MODEL STAGE 3—CONTROLLING 

This worker is 

applying a group

lock-out device. The

equipment cannot

be re-started until

all workers remove

their locks.
Section 8 Page 57

HAZARDS: SAFE WORK PRACTICES

Aworker was attempting to correct an electrical problem involving two non-operational lamps. He

examined the circuit in the area where he thought the problem was located. He had not shut off the

power at the circuit breaker panel and did not test the wires to see if they were live. He was electrocuted when he grabbed the two live wires with his left hand. He collapsed to the floor and was found

dead.

• Employers should not allow work to be done on electrical circuits unless an effective lock-out/tag-out

program is in place.

• No work should be done on energized electrical circuits. Circuits must be shut off, locked out, and

tagged out. Even then, you must test the circuit before beginning work to confirm that it is 

de-energized (“dead”).

277 VOLT LAMPS

FUSE BOX
To prevent injury when climbing, follow these procedures: 

1. Position the ladder at a safe angle to prevent slipping. The horizontal distance from the base of the ladder to the structure should

be one-quarter the length of the ladder. If you don’t have a way

to make this measurement, follow the steps below to determine if

the ladder is positioned at a safe angle. 

✔ Put your feet at the base of the ladder and extend your arms

straight out.

✔ If you can touch the closest part of the ladder without bending

your arms, the ladder is probably at the correct angle.

✔ If you have to bend your arms to touch the closest part of the 

ladder or if you can’t reach the ladder at all, the ladder is not

positioned at a safe angle. 

2. Make sure the base of the ladder has firm support and the ground

or floor is level. Be very careful when placing a ladder on wet,

icy, or otherwise slippery surfaces. Special blocking may be

needed to prevent slipping in these cases.

3. Follow the manufacturer’s

recommendations for 

proper use. 

4. Check the condition of the

ladder before using it. Joints

must be tight to prevent

wobbling or leaning. 

Page 58 Section 8 

Ladder Safety Fact Sheet
5. When using a stepladder, make sure it is level and fully open.

Always lock the hinges. Do not stand on or above the top step. 

6. When using scaffolding, use a ladder to access the tiers. Never

climb the cross braces.

7. Do not use metal ladders. Instead, use ladders made of fiberglass.

(Although wooden ladders are permitted, wood can soak up water

and become conductive.)

8. Beware of overhead powerlines when you work with ladders and

scaffolding.

Learn how to use ladders and scaffolding properly.

Section 8 Page 59
Page 60 Section 8 

SAFETY MODEL STAGE 3—CONTROLLING 

❑ Do not do any tasks that you are not trained to do or that you

do not feel comfortable doing!

Acrew of 7 workers was painting a 33-foot sign at a shopping mall. The crew used tubular 

welded frame scaffolding that was 31 feet tall and made up of several tiers. The sign was 

partially painted when the crew was instructed to move the scaffolding so that concrete could be

poured for an access road. The crew moved the scaffolding 30 feet without disassembling it. An overhead

powerline was located about 10 feet away from the scaffolding. After the concrete hardened, the workers lifted the scaffolding to move it back to the sign. The top tier came loose, fell, and contacted the powerline. All

seven workers were knocked away from the scaffolding. Two died; five were hospitalized.

You must take certain precautions when working with scaffolding.

• Scaffolding should not be moved until all potential safety hazards are identified and controlled. In this case,

the scaffolding should have been taken apart before it was moved.

• Locking pins must be used to secure tiers to one another.

• Always make sure you have enough time to complete your assignment safely. If you are rushed, you may

be more likely to take deadly short-cuts (such as failing to dismantle scaffolding before moving it).

• Employers must have a written safety program that includes safe work procedures and hazard recognition.

Acompany was contracted to install wiring and fixtures in a new office complex. The third floor was

being prepared in a hurry for a new tenant, and daily changes to the electrical system blueprints

were arriving by fax. The light fixtures in the office were mounted in a metal grid that was fastened

to the ceiling and properly grounded.

A 23-year-old male apprentice electrician was working on a light fixture when he contacted an energized

conductor. He came down from the fiberglass ladder and collapsed. Apparently, he had contacted the “hot”

conductor while also in contact with the metal grid. Current passed through his body and into the grounded grid. Current always takes a path to ground. In this case, the worker was part of that path.

He was dead on arrival at a nearby hospital. Later, an investigation showed that the victim had cross-wired

the conductors in the fixture by mistake. This incorrect wiring allowed electricity to flow from a live circuit

on the completed section of the building to the circuit on which the victim was working.

Below are some safety procedures that should have been followed in this case. Because they were

ignored, the job ended in death.

• Before work begins, all circuits in the immediate work area must be shut off, locked out, and tagged

out—then tested to confirm that they are de-energized.

• Wiring done by apprentice electricians should be checked by a journeyman.

• A supervisor should always review changes to an original blueprint in order to identify any new hazards

that the changes might create.
Section 8 Page 61

Avoid wet working conditions 

and other dangers

Remember that any hazard becomes much more dangerous in damp

or wet conditions. To be on the safe side, assume there is dampness

in any work location, even if you do not see water. Even sweat can

create a damp condition! 

❑ Do not work wet—Do not work on circuits or use electrical

equipment in damp or wet areas. If necessary, clear the area of

loose material or hanging objects. Cover wet floors with wooden

planking that can be kept dry. Wear insulating rubber boots or

shoes. Your hands must be dry when plugging and unplugging

power cords and extension cords. Do not get cleaning solutions

on energized equipment.

❑ Use a GFCI—Always use a GFCI when using portable tools and

extension cords.

Avoid overhead powerlines 

Be very careful not to contact overhead powerlines or other exposed

wires. More than half of all electrocutions are caused by contact

with overhead lines. When working in an elevated position near

overhead lines, avoid locations where you (and any conductive

object you hold) could contact an unguarded or uninsulated line.

You should be at least 10 feet away from high-voltage transmission

lines. 

Vehicle operators should also pay attention to overhead wiring.

Dump trucks, front-end loaders, and cranes can lift and make 

contact with overhead lines. If you contact equipment that is 

touching live wires, you will be shocked and may be killed. If you

are in the vehicle, stay inside. Always be aware of what is going on

around you. 

Use proper wiring and connectors 

❑ Avoid overloads—Do not overload circuits.

❑ Test GFCI’s—Test GFCI’s monthly using the “test” button.

❚ Avoid wet conditions! Even avoid

damp conditions!

HAZARDS: SAFE WORK PRACTICES

Portable GFCI.
Page 62 Section 8 

SAFETY MODEL STAGE 3—CONTROLLING 

❑ Check switches and insulation—Tools and other equipment

must operate properly. Make sure that switches and insulating

parts are in good condition.

❑ Use three-prong plugs—Never use a three-prong grounding

plug with the third prong broken-off. When using tools that

require a third-wire ground, use only three-wire extension cords

with three-prong grounding plugs and three-hole electrical outlets. Never remove the grounding prong from a plug! You could

be shocked or expose someone else to a hazard. If you see a cord

without a grounding prong in the plug, remove the cord from

service immediately. 

❑ Use extension cords properly—If an extension cord must be

used, choose one with sufficient ampacity for the tool being used.

An undersized cord can overheat and cause a drop in voltage and

tool power. Check the tool manufacturer’s recommendations for

the required wire gauge and cord length. Make sure the insulation

is intact. To reduce the risk of damage to a cord’s insulation, use

Aworker from an electrical service company was changing bulbs in pole-mounted light fixtures in a shopping center parking lot. The procedure for installing the bulbs was as follows: The worker would parkthe truck near the first light pole. The truck was equipped with a roof-mounted ladder. The worker would

extend the ladder high enough to change the bulb, then drive to the next pole without lowering the ladder.

After the worker replaced the first bulb, he got back in the truck and drove toward the next light pole. As the

truck moved along, a steel cable attached to the top of the ladder contacted an overhead powerline.The worker realized something was wrong, stopped the truck, and stepped onto the pavement while still holding onto

the door of the truck. By doing this, he completed the path to ground for the current in the truck. Because the

ladder was still in contact with the powerline, the entire truck was now energized. He was engulfed in flames

as the truck caught fire. Fire, police, and paramedic units arrived within 5 minutes. Utility workers arrived in

about 10 minutes and de-energized (shut off) the powerline. The victim burned to death at the scene.

Below are some ways to prevent contact with overhead powerlines.

• A safe distance must be maintained between ladders (and other equipment) and overhead lines. OSHA

requires that a clearance of at least 10 feet be maintained between aerial ladders and overhead powerlines

of up to 50,000 volts.

• Moving a truck with the ladder extended is a dangerous practice. One way to control this hazard is to install

an engine lock that prevents a truck’s engine from starting unless the ladder is fully retracted.

• If there are overhead powerlines in the immediate area, lighting systems that can be serviced from ground

level are recommended for safety.

• If the worker had been trained properly, he may have known to stay inside the truck.

• Pre-job safety surveys should always be performed to identify and control hazards. In this case, a survey

would have identified the powerlines as a possible hazard, and appropriate hazard control measures (such

as lowering the ladder between installations) could have been taken.

Never use a three-prong

grounding plug with the third

prong broken off.
cords with insulation marked “S” (hard service) rather than cords

marked “SJ” (junior hard service). Make sure the grounding

prong is intact. In damp locations, make sure wires and connectors are waterproof and approved for such locations. Do not 

create a tripping hazard.

❑ Check power cords and extensions—Electrical cords should be

inspected regularly using the following procedure:

1. Remove the cord from the electrical power source before

inspecting. 

2. Make sure the grounding prong is present in the plug.

3. Make sure the plug and receptacle are not damaged.

4. Wipe the cord clean with a diluted detergent and examine for

cuts, breaks, abrasions, and defects in the insulation.

5. Coil or hang the cord for storage. Do not use any other methods.

Coiling or hanging is the best way to avoid tight kinks, cuts, and

scrapes that can damage insulation or conductors.

You should also test electrical cords regularly for ground continuity

using a continuity tester as follows:

1. Connect one lead of the tester to the ground prong at one end

of the cord.

2. Connect the second lead to the ground wire hole at the other

end of the cord.

3. If the tester lights up or beeps (depending on design), the

cord’s ground wire is okay. If not, the cord is damaged and

should not be used.

❑ Do not pull on cords—Always disconnect a cord by the plug.

❑ Use correct connectors—Use electrical plugs and receptacles

that are right for your current and voltage needs. Connectors are

designed for specific currents and voltages so that only matching

plugs and receptacles will fit together. This safeguard prevents a

piece of equipment, a cord, and a power source with different

voltage and current requirements from being plugged together.

Standard configurations for plugs and receptacles have been

established by the National Electric Manufacturers Association

(NEMA).

Section 8 Page 63

HAZARDS: SAFE WORK PRACTICES
❑ Use locking connectors—Use locking-type attachment plugs,

receptacles, and other connectors to prevent them from becoming

unplugged. 

Use and maintain tools properly 

Your tools are at the heart of your craft. Tools help you do your job

with a high degree of quality. Tools can do something else, too.

They can cause injury or even death! You must use the right tools

for the job. Proper maintenance of tools and other equipment is very

important. Inadequate maintenance can cause equipment to deteriorate, creating dangerous conditions. You must take care of your tools

so they can help you and not hurt you.

❑ Inspect tools before using them—Check for cracked casings,

dents, missing or broken parts, and contamination (oil, moisture,

dirt, corrosion). Damaged tools must be removed from service and

properly tagged. These tools should not be used until they are

repaired and tested. 

❚ Maintain tools and equipment.

❚ Inspect your equipment before

you use it.

Page 64 Section 8 

Locking-type attachment plug.

This cord has been

spliced using a wire nut.

Spliced cords are very

dangerous!

SAFETY MODEL STAGE 3—CONTROLLING 
❑ Use the right tool correctly—Use tools correctly and for their

intended purposes. Follow the safety instructions and operating

procedures recommended by the manufacturer. When working on

a circuit, use approved tools with insulated handles. However,

DO NOT USE THESE TOOLS TO WORK ON 

ENERGIZED CIRCUITS. ALWAYS SHUT OFF

AND DE-ENERGIZE CIRCUITS BEFORE 

BEGINNING WORK ON THEM. 

❑ Protect your tools—Keep tools and cords away from heat, oil,

and sharp objects. These hazards can damage insulation. If a tool

or cord heats up, stop using it! Report the condition to a supervisor or instructor immediately. If equipment has been repaired,

make sure that it has been tested and certified as safe before

using it. Never carry a tool by the cord. Disconnect cords by

pulling the plug—not the cord!

❑ Use double-insulated tools—Portable electrical tools are classified by the number of insulation barriers between the electrical

conductors in the tool and the worker. The NEC permits the use

of portable tools only if they have been approved by

Underwriter’s Laboratories (UL Listed). Equipment that has two

insulation barriers and no exposed metal parts is called doubleinsulated. When used properly, double-insulated tools provide

reliable shock protection without the need for a third ground 

❚ Use the right tools and equipment.

❚ Do not work on energized circuits.

Section 8 Page 65

An employee was climbing a metal ladder to hand an electric drill to the journeyman installer on

a scaffold about 5 feet above him. When the victim reached the third rung of the ladder, he

received an electrical shock that killed him. An investigation showed

that the grounding prong was missing from the extension cord attached to

the drill. Also, the cord’s green grounding wire was, at times, contacting the

energized black wire. Because of this contact with the "hot" wire, the entire

length of the grounding wire and the drill’s frame became energized.The drill

was not double-insulated.

To avoid deadly incidents like this one, take these precautions:

• Make certain that approved GFCI’s or equipment grounding systems are

used at construction sites.

• Use equipment that provides a permanent and continuous path to ground.

Any fault current will be safely diverted along this path.

• Inspect electrical tools and equipment daily and remove damaged or 

defective equipment from use right away.

Don’t work on energized 

circuits like this one! 

Always follow correct 

lock-out/tag-out procedures.

HAZARDS: SAFE WORK PRACTICES
wire. Power tools with metal housings or only one layer of effective

insulation must have a third ground wire and three-prong plug.

❑ Use multiple safe practices—Remember: A circuit may not be

wired correctly. Wires may contact other “hot” circuits. Someone

else may do something to place you in danger. Take all possible

precautions.

Wear correct PPE

OSHA requires that you be provided with personal protective equipment. This equipment must meet OSHA requirements and be appropriate for the parts of the body that need protection and the work

performed. There are many types of PPE: rubber gloves, insulating

shoes and boots, face shields, safety glasses, hard hats, etc. Even if

laws did not exist requiring the use of PPE, there would still be

every reason to use this equipment. PPE helps keep you safe. It is

the last line of defense between you and the hazard. 

❚ Wear and maintain PPE.

Page 66 Section 8 

A22-year-old male carpenter was building the wooden framework of a laundry building. He was using

portable power tools. Electricity was supplied to the tools by a temporary service pole 50 feet away.

The service pole had not been inspected and was not in compliance. It was also not grounded. The

carpenter plugged a “homemade” cord into the service pole and then plugged a UL-approved cord into the

homemade cord. His power saw was plugged into the UL-approved cord.

The site was wet. Humidity was high and the carpenter was sweating. Reportedly, he was mildly shocked

throughout the morning and replaced the extension cord he was using in an effort to stop the shocks. At one

point, as he was climbing down a makeshift ladder constructed from a floor truss, he shifted the power saw

from his right hand to his left hand and was shocked. He fell from the ladder into a puddle of water, still holding the saw. The current had caused his hand to contract, and he was “locked” to the saw. A co-worker 

disconnected the power cord to the saw. CPR was given, but the shock was fatal.

Attention to these general safety principles could have prevented this death.

• Any and all electrical equipment involved in a malfunction should be taken out of service immediately. The

carpenter should have taken the saw out of service, not just the extension cord. (As it turns out, the saw

was the source of the shocks, not the cord.)

• Although the homemade extension cord does not seem to have contributed to this incident, it should not

have been used.

• The floor truss should not have been used as a ladder. For climbing, use only approved ladders or other

equipment designed specifically for climbing.

• Do not work in wet areas. The water should have been removed from the floor as soon as it was found.

Humidity and perspiration can also be hazards. Try to stay as dry as possible, be alert, and take action to

protect yourself when needed.

• OSHA requires that all receptacles at construction sites that are not part of the permanent wiring have

GFCI’s.

• Be aware that shocks can cause you to lose your balance and fall, often resulting in more severe injury.

SAFETY MODEL STAGE 3—CONTROLLING 
❑ Wear safety glasses—Wear safety glasses to avoid eye injury.

❑ Wear proper clothing—Wear clothing that is neither floppy nor

too tight. Loose clothing will catch on corners and rough surfaces. Clothing that binds is uncomfortable and distracting.

❑ Contain and secure loose hair—Wear your hair in such a way

that it does not interfere with your work or safety.

❑ Wear proper foot protection—Wear shoes or boots that have

been approved for electrical work. (Tennis shoes will not protect

you from electrical hazards.) If there are non-electrical hazards

present (nails on the floor, heavy objects, etc.), use footwear that

is approved to protect against these hazards as well. 

❑ Wear a hard hat—Wear a hard hat to protect your head from

bumps and falling objects. Hard hats

must be worn with the bill forward

to protect you properly.

❑ Wear hearing protectors—Wear

hearing protectors in noisy areas to

prevent hearing loss.

❑ Follow directions—Follow the

manufacturer’s directions for cleaning and maintaining PPE. 

❑ Make an effort—Search out and

use any and all equipment that will

protect you from shocks and other

injuries.

❚ Think about what you are doing.

❚ PPE is only effective when used

correctly.

Section 8 Page 67

Wear safety glasses to avoid eye injury.

Arcing electrical burns

through the victim’s

shoe and around the

rubber sole.

Don’t wear hard

hats backwards!

HAZARDS: SAFE WORK PRACTICES
Page 68 Section 8 

PPE is the last line of defense against workplace hazards. OSHA defines PPE as "equipment for 

the eyes, face, head, and extremities, protective clothing, respiratory devices, protective shields and

barriers." Many OSHA regulations state that PPE must meet criteria set by the American National

Standards Institute (ANSI).

Head Protection

OSHA requires that head protection

(hard hats) be worn if there is a risk of

head injury from electrical burns or falling/flying

objects. 

Aren’t all hard hats the same?

No. You must wear the right hat for the job. All hard

hats approved for electrical work made since 1997

are marked "Class E." Hard hats made before 1997

are marked "Class B." These markings will be on a

label inside the helmet or stamped into the helmet

itself. Newer hats may also be marked "Type 1" or

"Type 2." Type 1 hard hats protect you from impacts

on the top of your head. Type 2 hard hats protect

you from impacts on the top and sides of your head.

How do I wear and care for my

hard hat?

Always wear your hat with the bill forward. (Hats

are tested in this position.) If you wear a hat differently, you may not be fully protected. The hat

should fit snugly without being too tight. You should

clean and inspect your hard hat

regularly according to the manufacturer’s instructions. Check

the hat for cracks, dents, frayed

straps, and dulling of the 

finish. These conditions can

reduce protection. Use only

mild soap and water for cleaning. Heavy-duty cleaners and

other chemicals can damage

the hat. 

HEAD PROTECTION

Class E, Type 1 hard hat. Class B hard hat.

Don’t wear another hat

under your hard hat!

PPE Fact Sheet—The Right Equipment—Head to 
Section 8 Page 69

Do not "store" anything (gloves, wallet, etc.) in the

top of your hard hat while you are wearing it. The

space between the inside harness and the top of the

hard hat must remain open to protect you. Do not

put stickers on your hat (the glue can weaken the 

helmet) and keep it out of direct sunlight. If you

want to express your personality, hard hats come in

many colors and can be imprinted with custom

designs by the manufacturer. Some hats are available in a cowboy hat design or with sports logos. 

Use your head and protect your head!

Never “store” anything in the top

of your hard hat while you are

wearing it.

Class B hard hat in a cowboy

hat design.

Keep your hard hat out of direct sunlight when you are not wearing it!

Toe
Foot Protection

Workers must wear protective footwear

when there is a risk of foot injury from

sharp items or falling/rolling objects—

or when electrical hazards are present. As

with hard hats, always follow the manufacturer’s instructions for cleaning and maintenance of footwear. Remember that cuts, holes, worn

soles, and other damage can reduce protection. 

How do I choose the 

right footwear? 

The footwear must be ANSI approved. ANSI

approval codes are usually printed inside the tongue

of the boot or shoe. Footwear will be marked "EH"

if it is approved for electrical work. (The ANSI 

approval stamp alone does not necessarily mean the footwear offers protection from electrical hazards.) Note that

footwear made of leather must be kept

dry to protect you from electrical hazards, even if it is marked "EH."

What about non-electrical 

hazards? 

All ANSI approved footwear has a protective toe

and offers impact and compression protection. But

the type and amount of protection is not always the

same. Different footwear protects you in different

ways. Check the product’s labeling or consult the

manufacturer to make sure the footwear will 

protect you from the hazards you face. 

FOOT PROTECTION

Don’t take risks because you are wearing PPE.

PPE is the last line of defense against injury! 

C = Compression rating

[This code is more complex than

the others. Here is how to read it:

30 = 1,000 pounds;

50 = 1,750;

75 = 2,500 (in this example)] 

MT = Metatarsal (top of the foot)

protection rating (75 foot pounds in

this example—can also be 30 or 50)

ANSI Z41 = ANSI footwear

protection standard

PT = Protective Toe section

of the standard

91 = year of the standard

(in this example 1991)

M = Male footwear

(F = Female footwear)

I = Impact rating

(75 foot pounds in

this example—can

also be 30 or 50)

Page 70 Section 8 

PPE Fact Sheet (continued)

SAFETY MODEL STAGE 3—CONTROLLING
Summary of Section 8 

Control hazards through safe work practices.

Plan your work and plan for safety.

Avoid wet working conditions and other dangers.

Avoid overhead powerlines. 

Use proper wiring and connectors. 

Use and maintain tools properly. 

Wear correct PPE.

Section 8 Page 71

 HAZARDS: SAFE WORK PRACTICES
Page 72

Glossary of Terms 

ampacity

maximum amount of current a wire can carry safely without overheating 

amperage

strength of an electrical current, measured in amperes

ampere (amp)

unit used to measure current 

arc-blast

explosive release of molten material from equipment caused by

high-amperage arcs

arcing

luminous electrical discharge (bright, electrical sparking) through

the air that occurs when high voltages exist across a gap between

conductors 

AWG

American Wire Gauge—measure of wire size

bonding

joining electrical parts to assure a conductive path

bonding jumper

conductor used to connect parts to be bonded

circuit

complete path for the flow of current 

circuit breaker

overcurrent protection device that automatically shuts off the current

in a circuit if an overload occurs 

conductor

material in which an electrical current moves easily 

CPR

cardiopulmonary resuscitation—emergency procedure that involves

giving artificial breathing and heart massage to someone who is not

breathing or does not have a pulse (requires special training)

current

movement of electrical charge

de-energize

shutting off the energy sources to circuits and equipment and 

depleting any stored energy

double-insulated

equipment with two insulation barriers and no exposed metal parts

energized (live, “hot”)

similar terms meaning that a voltage is present that can cause a 

current, so there is a possibility of getting shocked

fault current

any current that is not in its intended path
Page 73

Glossary of Terms (continued)

fixed wiring

permanent wiring installed in homes and other buildings

flexible wiring

cables with insulated and stranded wire that bends easily

fuse 

overcurrent protection device that has an internal part that melts and

shuts off the current in a circuit if there is an overload

GFCI

ground fault circuit interrupter—a device that detects current 

leakage from a circuit to ground and shuts the current off

ground

physical electrical connection to the earth

ground fault

loss of current from a circuit to a ground connection 

ground potential

voltage a grounded part should have; 0 volts relative to ground 

guarding

covering or barrier that separates you from live electrical parts

insulation

material that does not conduct electricity easily

leakage current

current that does not return through the intended path, but instead

"leaks" to ground 

lock-out

applying a physical lock to the energy sources of circuits and equipment after they have been shut off and de-energized

milliampere (milliamp or mA)

1/1,000 of an ampere

NEC

National Electrical Code—comprehensive listing of practices to protect workers and equipment from electrical hazards such as fire and

electrocution

neutral

at ground potential (0 volts) because of a connection to ground

ohm

unit of measurement for electrical resistance 

OSHA

Occupational Safety and Health Administration—Federal agency in

the U.S. Department of Labor that establishes and enforces workplace safety and health regulations
Page 74

Glossary of Terms (continued)

overcurrent protection device

device that prevents too much current in a circuit

overload

too much current in a circuit

power

amount of energy used each second, measured in watts 

PPE

personal protective equipment (eye protection, hard hat, special

clothing, etc.)

qualified person

someone who has received mandated training on the hazards and on

the construction and operation of equipment involved in a task

resistance

material’s ability to decrease or stop electrical current

risk

chance that injury or death will occur

shocking current

electrical current that passes through a part of the body 

short

low-resistance path between a live wire and the ground, or between

wires at different voltages (called a fault if the current is unintended)

tag-out

applying a tag that alerts workers that circuits and equipment have

been locked out

trip

automatic opening (turning off) of a circuit by a GFCI or circuit

breaker

voltage

measure of electrical force

wire gauge

wire size or diameter (technically, the cross-sectional area)

Endnotes 

1. Castillo DN [1995]. NIOSH alert: preventing death and injuries of adolescent

workers. Cincinnati, OH: U.S. Department of Health and Human Services,

Public Health Service, Centers for Disease Control and Prevention, National

Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 

No. 95-125. 

2. Lee RL [1973]. Electrical safety in industrial plants. Am Soc Safety Eng J

18(9):36-42.

3. DOL [1997]. Controlling electrical hazards. Washington, DC: U.S. Department

of Labor, Occupational Safety and Health Administration.
Appendix 

OSHA Standards

OSHA occupational safety and health standards for General

Industry are located in the Code of Federal Regulations (CFR),

Title 29, Part 1910 (abbreviated as 29 CFR 1910). Standards

for Construction are located in Part 1926 (abbreviated as 29

CFR 1926). The full text of these standards is available on

OSHA's Web site: www.osha.gov. 

OSHA standards related to electrical safety for General

Industry are listed below: 

Subpart S—Electrical 

GENERAL

1910.301 - Introduction 

DESIGN SAFETY STANDARDS FOR ELECTRICAL SYSTEMS

1910.302 – Electric utilization systems

1910.303 – General requirements 

1910.304 – Wiring design and protection 

1910.305 – Wiring methods, components, and equipment for

general use

1910.306 – Specific purpose equipment and installations

1910.307 – Hazardous (classified) locations

1910.308 – Special systems

SAFETY-RELATED WORK PRACTICES

1910.331 – Scope 

1910.332 – Training 

1910.333 – Selection and use of work practices 

1910.334 – Use of equipment

1910.335 – Safeguards for personnel protection

Subpart J—General Environment Controls 

1910.147 – The control of hazardous energy (lock-out/tag-out)

1910.147 – Appendix A—Typical minimal lock-out 

procedures 

Subpart R—Special Industries

1910.268 – Telecommunications

1910.269 – Electric power generation, transmission, and distribution

OSHA standards related to electrical safety for Construction are

listed below: 

Subpart K—Electrical

GENERAL

1926.400 – Introduction 

INSTALLATION SAFETY REQUIREMENTS

1926.402 – Applicability

1926.403 – General requirements

1926.404 – Wiring design and protection

1926.405 – Wiring methods, components, and equipment for

general use

1926.406 – Specific purpose equipment and installations

1926.407 – Hazardous (classified) locations

1926.408 – Special systems

SAFETY-RELATED WORK PRACTICES

1926.416 – General requirements

1926.417 – Lock-out and tagging circuits 

SAFETY-RELATED MAINTENANCE AND ENVIRONMENTAL

CONSIDERATIONS

1926.431 – Maintenance of equipment 

1926.432 – Environmental deterioration of equipment

SAFETY REQUIREMENTS FOR SPECIAL EQUIPMENT

1926.441 – Batteries and battery charging

DEFINITIONS

1926.449 – Definitions applicable to this subpart

Subpart V—Power Transmission and

Distribution

1926.950 – General requirements

1926.951 – Tools and protective equipment

1926.952 – Mechanical equipment

1926.953 – Material handling

1926.954 – Grounding for protection of employees

1926.955 – Overhead lines

1926.956 – Underground lines

1926.957 – Construction in energized substations

1926.958 – External load helicopters

1926.959 – Lineman's body belts, safety straps, and lanyards

1926.960 – Definitions applicable to this subpart 

Page 75
Page 76

A

aluminum wire hazard 24

amp 6

ampacity 24

ampere 6

arc-blast 12

arc-fault circuit breaker 46

arcing 12, 29

arthritis 30

AWG 39

B

bonding 49

bonding jumper 50

burns, arc 12, 15

burns, electrical 6, 10, 12, 15

burns, thermal contact 12, 15

C

cable, 240v 4

cardiopulmonary resuscitation 17

carpal tunnel syndrome 31

circuit 2

circuit breaker 29, 34, 50

circuit breaker, and leakage current 28

clearance distance 26

clues of electrical hazards 34 

clues,

blown fuses 34

tripped circuit breakers 34

tripped GFCI 35

warm extension cord 34

warm junction box 35

warm tools and wire 34

worn insulation 35

Code of Federal Regulations 75

concussion 12

conductor 3

controlling hazards 19, 21, 36, 54

CPR (see cardiopulmonary 

resuscitation)

CFR (see Code of Federal Regulations)

current,

calculating 42

current 2

effects on body 7

path through body 8, 9, 10

current leakage 47

cuts 31

D

de-energizing circuits 55

E

electrical hazards,

aluminum wire 24

damaged hand tool 31, 34

damaged tool 29

defective insulation 26

exposed electrical parts 24

improper grounding 27

inadequate wiring 24

overhead powerline 25

overload 28

wet conditions 29

electrical shock,

amount 6, 11

current density 9

duration 6, 7, 11

path 8, 9, 10, 11

receiving 2

electrical shock—what to do for 16

electrocution, deaths 1, 7, 10

energized 2

evaluating hazards 19, 21, 34

evaluating risk 34

extension cord 24, 34, 42, 46, 63

F

falls 56

fault 27

fault, low current 47

fire extinguisher, types 14

fires, electrical 14, 24, 28, 29

fires—what to do 14

fixed wiring 40

flexible wiring 41

foot protection 70

freezing 6

fuse 29, 34, 51

G

GFCI 

(see ground fault circuit interrupter)

ground 2

ground connection 47

ground fault 28

ground fault circuit interrupter

28, 34, 48, 61

ground potential 27

grounding 27, 28, 46

grounding path 47

guarding 43

H

hard hat 68

hazards (also see electrical hazards),

chemical 30

control (see controlling hazards)

falling objects 32

falls 32

inadequate wiring 24

lifting 32

overhead work 30

particles 32

hazardous environments 51

I

impedance 8

insulation 26, 44

insulation damage 45

isolation 43

J

jewelry 56

jumper, bonding 49

K

kill switches 17

L

ladder safety 58

leakage current 28

live 2

lock-out/tag-out 37, 38

lock-out/tag-out checklist 38

low back pain 31

INDEX
Page 77

M

mA 6

milliamp 6

milliampere 6

N

National Electrical Code 15

National Electrical Safety Code 19

NEC (see National Electrical Code)

NEMA 63

NESC (see National Electrical 

Safety Code

nonconductive material 28

O

Occupational Safety and Health

Administration 15

ohm 8

OSHA (see Occupational Safety and

Health Administration)

overhead power lines 25, 61

overload 28

P

personal protective equipment

31, 66, 68, 80

perspiration 30

plugs, three-prong 62

power 42

power rating 42

PPE 

(see personal protective equipment)

R

recognizing hazards 18, 21, 22

resistance 8

resistance, effect on current 8

respiratory paralysis 6

risk 34

risk evaluation 34

S

safe work environment 19, 36

safe work practices 19, 54

safety model, overview 18

shock (see electrical shock)

shocking current 6

short 34

T

tendinitis 30

tools 64

tools, double-insulated 65

V

ventricular fibrillation 6

voltage,

high 7, 12

low 6

voltage 2

W

wet conditions 29, 61

wire gauge 24

wire size 24

INDEX

©P. Barber/CMSP—9 

Richard Carlson—23a, 26b, 57, 65a

©Corbis Images—6

©M. English/CMSP—10

Thaddeus W. Fowler—34, 46a, 47a, 51

Cat Goldberg—cover, 5, 20, 25a, 26a, 27, 30, 31,

32a, 37a, 38ab, 43c, 49, 50, 55, 56, 58b, 59a,

64b, 65b, 67ac, 68abc, 69ac, 70

Karen K. Miles—14bc, 18, 19, 23b, 24, 25b,

37b, 39, 48, 58c, 61, 62, 64a, 69b

©PhotoDisc—1, 2, 3, 8, 14a, 28ab, 29, 32b, 40,

43a, 44, 46b, 47b, 58a, 59bc, 66

©PhotoQuest—25c, 43b

R.K.Wright, M.D.—www.emedicine.com

12, 67b

Photo and Graphics Credits


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Fax number: (513) 533-8573

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or visit the NIOSH Web site at www.cdc.gov/niosh

DHHS (NIOSH) Publication No. 2002-123

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