Module 2: Electrical Safety

Module Description

OSHA’s electrical standards were put in place to help minimize deaths and injuries from dangers such as electrocution, burns, electric shock, fires, and explosions. This 2-hour interactive online course examines the main causes of different types of hazards and details precautions for preventing accidents. It looks specifically at the requirements of 29 CFR 1926, Subpart K – which covers the design characteristics of safe systems for use when installing and using electrical systems. While workers may need additional training based on OSHA standards and the specific hazards of their jobs, RedVector’s Worksite Safety courses can help inject entry-level workers with critical knowledge on a variety of OSHA-regulated safety and health topics.

Learning Objectives

Upon completion of this module, students should be able to:

• Identify major electrocution hazards
• Describe types of electrocution hazards
• Protect him/herself from electrocution hazards
• Recognize employer requirements to protect workers from electrocution hazards

Introduction

While it is common knowledge that electricity is a ubiquitous power source for everything from light bulbs to power tools to critical medical applications, not much attention is paid to the significant hazards it presents when people work in close proximity with it or with it directly. This is especially true at places like construction sites, where there are often a number of temporary electrical power sources set up to power a host of tools, lighting, fans, pumps, and other equipment.
Engineers, power line workers, and electronic technicians – to name a few – work directly with electricity. Others – workers who use power tools, construction crews building near overhead wires – work with it indirectly.
OSHA’s electrical standards were put in place to help minimize deaths and injuries from dangers such as electrocution, burns, electric shock, fires, and explosions. The standard specifies design characteristics of safe systems for use when installing and using electrical systems. We will be looking specifically at the requirements of 29 CFR 1926 Subpart K – Electrical (1926.400 to 1926.449).
The Occupational Safety and Health Administration (OSHA) recognized the important role of the National Electrical Code (NEC) in defining basic requirements for safety in electrical installations by including the entire 1971 NEC by reference in Subpart K of 29 Code of Federal Regulations Part 1926 (Construction Safety and Health Standards). In the final ruling of July 11, 1986, OSHA updated, simplified, and clarified Subpart K, 29 CFR 1926. This eliminated the need to continually reference the NEC and made the standard easier for employers and employees to use and understand. The OSHA revision is also more flexible, eliminating the need to continually keep pace with the NEC. The National Fire Protection Association is responsible for the NEC, which is referred to as NFPA 70. The most updated codes can be found at www.nfpa.org.
The NEC provisions directly related to employee safety are included in the body of the standard itself — making it unnecessary to continue the adoption by reference of the NEC. Subpart K is divided into four major groups plus a general definitions section:

• Installation Safety Requirements [29 CFR 1926.402 – 1926.415]
• Safety-Related Work Practices [29 CFR 1926.416 – 1926.430]
• Safety-Related Maintenance and Environmental Considerations [29 CFR 1926.431 – 1926.440]
• Safety Requirements for Special Equipment [29 CFR 1926.441 – 1926.448] Definitions [29 CFR 1926.449]

You can find out more about the specific sections of Subpart K by clicking on the links on the above items, and we will cover more about each section later in the course in the third section, General Planning and Controls. For now, we will concentrate on the following:

• Overview – How electricity works, and why it is dangerous
• Hazard/Controls – What the main hazards are and the best ways to prevent them from occurring

Overview

Wherever there is wide use of electrical circuits, portable power tools and flexible extension cords – such as on a construction site – workers face the risk of encountering electrical hazards, particularly electrical shock. Cords, connectors, receptacles, and other electrical equipment must be properly maintained or it can become hazardous; flexible cords are in general more easily (and more often) damaged than fixed wiring.
In 2010, 76 workers were killed by electrocutions on the job. Statistically, electrical accidents cause nearly 10 percent of workplace fatalities. The truly tragic part is that many of these fatalities could have easily been avoided. The aim of this course is to help you recognize electrical hazards and thus help prevent accidental death and injuries.

What Electricity Is

Electricity is the flow of energy from one place to another. It is comprised of electrons that travel through a conductor in a closed circuit, and requires a source of power – such as a generator. Operating an electric switch is a lot like turning on a water faucet.

What Affects the Flow of Electricity

Conductors – such as metals – are materials that offer little resistance to the flow of electric current. Conductors can be (a) bare – a conductor having no covering or electrical insulation whatsoever. (b) covered – a conductor encased within material of composition or thickness that is not recognized as electrical insulation. (c)insulated – a conductor encased within material of composition and thickness that is recognized as electrical insulation.
Insulators – such as porcelain, glass or dry wood – slow the flow of electricity.
Some materials may most often act as either an insulator (i.e., air) or a conductor (impure water), but under certain circumstances can change from one to the other. For instance, air is normally an insulator, but conducts lightning under the right conditions. Dry wood is normally an insulator, but if you wet it, it becomes a conductor. Pure water is not a good conductor – but once impurities are introduced, it becomes a good conductor.

Electrical Terms

• Volts – electrical pressure (measure of electrical force)
• Amps – the volume or intensity of the electrical flow
• Watts – the power consumed
• Current – electrical movement (measured in amps)
• Circuit – the complete path of the current. Includes the electricity source, the conductor, and the output device (such as a tool, light, etc.)
• Resistance – measured in ohms; the resistance of a material to the flow of electricity
• Conductors – materials with little resistance
• Grounding – a conductive connection to the earth that acts as a protective measure
• Insulators – materials with high resistance to electricity; often used to prevent electricity from getting to unwanted places

Types of Electrical Injuries

There are four main types of electrical injuries:

• Electrocution
• Electrical shock
• Burns
• Indirect injuries (i.e., a fall from a ladder caused by a shock)

Electrocution

Electrocution is a severe electrical shock. The victim suffers the most severe symptoms of contact with electricity and may suffer burns, nerve damage, muscle contractions, cardiac arrest, paralysis, and more. Electrocution most often involves internal and external harm to the body and does result in death.

Electrical Shock

What Causes a Shock?

A shock occurs when your body offers the path of least resistance for completing a circuit.
Shocks can occur when your body completes the path with:

• Both wires of an electric circuit
• One wire of an energized circuit and the ground
• A metal part that accidentally becomes energized
• Another “conductor” that is carrying a current

Electricity travels in closed circuits, and its normal route is through a conductor. Electric shock occurs when the body becomes part of the circuit.
When a shock enters the body, it can produce several types of injuries. Electrocution most often involves internal and external harm to the body and does result in death.
If an individual is not killed by that initial jolt, all or part of the body may be paralyzed, either temporarily or permanently. The heart’s rhythms may be disrupted, and the victim may lose the ability to grip or stand. Involuntary movements are also seen often, as are external and/or internal burns.
An electric shock can feel like anything from a slight tingling to immediate heart failure.
A shock’s severity depends on:

• The amount of current
• The current’s path
• The length of time
• The current’s frequency

1 milliamp (mA) – The approximate level of static shock, like you might get when you touch metal after walking across a carpet on a dry day. Almost never painful, and cannot damage the human body.
5 mA – This is a slight electrical shock that may tingle, but probably won’t be terribly painful. Safety devices called Ground Fault Circuit Interrupters (GFCIs) trip at 5 mA, so in many cases a GFCI-protected circuit will not deliver a dangerous shock.
10 mA – This is the average strength at which a shock will probably test your pain threshold. At this level, you could lose control of your muscles – a dangerous situation if you are on a scaffold or ladder.
50 – 150 mA – A shock from this much current will be extremely painful and can cause serious burns, respiratory arrest, cardiac fibrillation (disrupting your heartbeat) and severe muscle contractions. Some shocks this powerful can be fatal.
1,000 – 4,300 mA – This level of current is rarely encountered if safety measures are in place. This degree of shock causes fibrillation, paralysis, and permanent nerve damage at the least – and death is likely.
10,000 mA – This shock is almost sure to kill you, but if it doesn’t, it will cause complete cardiac arrest, severe burns, nerve damage, and paralysis.

Why Workers at Risk for Shock

Electrical accidents are usually caused by a combination of three factors:

• Unsafe equipment and/or installation
• Workplaces made unsafe by the environment (think electrical equipment in a rain storm)
• Unsafe work practices

The metal parts of tools or machines may become energized if there is a cut or fraying in the insulation or power cord of a tool or in the wiring of a machine.
Workers may come in contact with overhead power lines unintentionally because of carelessness or misgauging the overhead distance to the line.
Lightning is a particular threat when working outdoors on high-rise scaffolding or equipment, though its current can also travel through simple household appliances or workman’s tools.

Burns

Electrical burns are the most common shock-induced injury, with three types of varying intensity and severity:

• Electrical burns occur when heat is generated by the flow of electrical current through the body, thus causing tissue damage. This is one of the most serious burns and requires immediate medical attention.
• Arc or flash burns occur when an electrical arc or explosion with enough intensity to burn someone nearby.
• Thermal contact burns are caused by skin coming in contact with overheated electrical equipment, or when clothing ignites from a spark or other electrical incident.

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Case Study

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.
Source: CDC Workplace Safety & Health, Electrical Safety, Safety and Health for Electrical Trades Student Manual, http://www.cdc.gov/niosh/pdfs/02-123.pdf

How the Death Could Have Been Prevented

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 lockout/tag-out, and test circuits and equipment to make sure they are deenergized.
• 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.

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Indirect Injuries

Electric shock can cause indirect injuries from falls. For one thing, when you receive a shock, you’re – well – shocked, and may lose your balance on a ladder even if only from surprise. For another, if the shock is severe enough, you may lose muscle function and fall because you’re at least temporarily paralyzed.

General Information

• When electrical shock is sufficient to cause muscle contraction, the “freezing” effect makes it impossible for the person to pull free from the energy source. The current must be shut off immediately to release them!
• Static electricity can also cause a shock, and while the kind you get after shuffling across a carpet is generally mild, static electricity can build up and discharge to an object with very serious consequences. Grounding or other measures are often necessary to prevent static electricity buildup.
• The longer the exposure to the current, the greater the danger.
• Low voltage does not mean low hazard!
• A severe shock often causes more damage than that initially visible: There may be internal hemorrhaging and tissue and nerve damage.

Hazards and Controls

Recognizing and Controlling Electrical Hazards

Exposed electrical parts, wet conditions, damaged equipment and tools, improper personal protective equipment, overloaded circuits, improperly grounded electrical devices, defective insulation and inadequate wiring are some of the usual suspects when an electrical accident occurs.
There are also “clues” that electrical hazards exist:

• A ground fault circuit interrupter keeps tripping
• Circuit breakers trip and fuses blow, which show that too much current is flowing. This could be due to a number of factors, such as malfunctioning equipment or a short between conductors.
• An electrical tool, wire, or connection that feels warm may indicate too much current in the circuit or equipment.
• An extension cord that feels warm may indicate too much current for the wire size of the cord.
• A cable, fuse box or junction box that feels warm may indicate too much current in the circuits
• A burning odor, which may indicate overheated insulation
• Worn, frayed or damaged insulation around wires or conductors is an electrical hazard because the conductors could be exposed. Contact with an exposed wire could cause a shock, and damaged insulation could cause a short, leading to arcing or a fire.

The two best means of avoiding injury from electrical devices are insulation and grounding.
Insulation – Conductor insulation may be provided by placing nonconductive material such as plastic around a conductor. Insulators help stop or reduce the flow of electrical current, which in turn helps prevent shocks, short circuits and fires. Insulated conductor wires used in equipment grounding are usually either green or green with yellow stripes.
Grounding means establishing a direct connection to a known ground, such as the earth. Grounding creates a low-resistance path from a device to the earth to disperse unwanted current harmlessly. It prevents the buildup of voltages that might lead to an accident. While grounding is a good safety measure, it is a preventive measure and won’t guarantee against a shock. Grounded conductors are usually white-coated wires.
Ungrounded conductors – or hot wires, be any color other than green, white, or gray, but they are usually black or red! Regardless of the color, verify the energy has been isolated(turned off) prior to contacting.
Proper grounding is essential, but doesn’t replace knowledge! It’s important to note that standard 120-volt circuits usually have two wires: A black “hot” wire and a white wire that is neutral and connected to ground. Touching the black wire will cause a shock!
240-volt circuits usually have two wires also. One carries a potential +120 volts; the other is – 120 volts. Touching both of these wires at once will cause a potentially fatal shock!
One measure of control is to isolate electrical parts using guards or barriers and by replacing covers. CFR 1926.403(i)(2) states that “live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by cabinets or other forms of enclosures…”
Electrical junction boxes and motor housings are both good examples of using barriers to protect equipment and people.
If a “hot” wire contacts a grounded enclosure, a ground fault results – a condition that trips circuit breakers and blows fuses. Any time you touch part of an electrical circuit, you can sustain a shock if there is a ground fault and your body unwittingly becomes the easiest path to ground.

Prevention

To prevent your body from becoming the easiest path to ground, a ground fault circuit interrupter (GFCI) can interrupt the circuit and prevent the current from reaching you. The OSHA standard for the construction industry requires the use of GFCIs (more on this important device later).
Other preventive measures, as outlined in 1926.405(b)(1) cover conductors entering boxes, cabinets or fittings, stating they “shall be protected from abrasion, and openings through which conductors enter shall be effectively closed.”
Also detailed are covers and canopies, with the standard stating: “All pull boxes, junction boxes, and fittings shall be provided with covers. If metal covers are used, they shall be grounded.”

Overhead and Buried Power Lines

These power lines are particularly hazardous because they carry extremely high voltages and are usually not insulated.
Punished by Power!

• Crane
• Ladder
• Scaffolding
• Backhoe
• Scissors lift
• Raised dump truck bed

The main risk from contact with a power line is deadly electrocution. Next are burns and falls from the elevation one might be at working near a line. Finally, using tools and equipment that are liable to come in contact with power lines increases the risk of an accident.
Surprisingly, more than 50 percent of electrocutions are caused by a worker coming in direct contact with energized power lines.

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Case Study

A 38-year-old lineman standing in an aerial bucket was electrocuted while repairing a 13.2-kilovolt power line that had been damaged during an electrical storm. The damaged line was one of two power lines that served a residential area. A third power line supplied a three-phase transformer that served a store and was also internally connected with the other two power lines.
To repair the damaged line, both of the residential power lines were presumed deenergized by opening their respective fused disconnects. However, the third line remained energized to provide power to the store. Voltage back-fed through the transformer on this line and inadvertently energized the line on which a splice was to be made.
Not surprisingly, power line workers face the most risk. Eighty percent of all lineman deaths were at one time attributed to a worker touching a live wire with his/her hand; now, all linemen wear special gloves that protect them from voltages up to 34,500. The majority of today’s power line accidents occur because of failure to maintain proper work distances.
Overhead wires must be deenergized and grounded (or other safeguards put in place) before anyone works with them.
Workers also need to wear (and be trained in the use of) special Personal Protective Equipment (PPE).
Besides PPE, other vital methods of protection when working around power lines include:

• Post warning signs near overhead power lines and buried power line indicators
• Contact utilities for buried power line locations
• Stay at least 10 feet away from overhead lines
• Assume that lines are energized unless you’ve established otherwise
• Have the lines’ owner or operator deenergize them before work begins on them
• Use wood or fiberglass ladders in lieu of metal

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Are You Wired?

Improper or inadequate wiring is another opportunity for electrical disaster. And an electrical hazard is created when, for instance, a wire is too small a gauge for the amount of current it will carry.

What Can Go Wrong If the Wiring Is Inadequate

An example would be using a portable tool with an extension cord that is too small for the tool. The cord will draw more current than the cord can handle, and the cord could overheat or even cause a fire without tripping the circuit breaker.
Using the correct wire – which will be determined by the operation it is intended for, the building materials it will be used with, the electrical loads, and environmental factors – will forestall most electrical wiring hazards. Fixed cords should be used when possible as they are sturdier than flexible cords. The OSHA standard requires flexible cords to be rated for hard or extra-hard usage, and they must be indelibly marked as such approximately 12 inches for the length of the cord.

Defective Cords & Wires

Damaged insulation – whether due to age, accidental cuts, abrasion, etc. – can turn a seemingly benign power cord or wire into a silent, deadly floor snake. In all seriousness, when insulation is cut, frayed or otherwise damaged and the inner wires are exposed, the metal parts of a device may become energized if a live wire inside touches them, and if you touch damaged equipment or the damaged portion of the cord, you can receive a shock.
To protect you from harm due to the poor condition of cords and wires:

• Insulate live wires
• Check before use
• Use only 3-wire-type cords
• Use only cords marked for hard or extra-hard usage
• Make sure your cords are equipped with strain-relief
• Unplug cords by grasping the plug, not pulling the cord
• Take unmarked or modified cords out of service

The NEC and OSHA have specified particular types of flexible cords for use in a construction environment. This rule designates what type of cords must be used for such applications as lights and portable tools.
Hazards are created when cords, cord connectors, receptacles, and cord- and plug-connected equipment are improperly used and maintained. Flexible cords must be connected to devices and to fittings so as to prevent tension at joints and terminal screws. Because a cord is exposed, flexible, and unsecured, joints and terminals become more vulnerable. Flexible cord conductors are finely stranded for flexibility, but the strands of one conductor may loosen from under terminal screws and touch another conductor, especially if the cord is subjected to stress or strain.
A flexible cord may be damaged by activities on the job, by door or window edges, by staples or fastenings, by abrasion from adjacent materials, or simply by aging. If the electrical conductors become exposed, there is a danger of shocks, burns, or fire. A frequent hazard on a construction site is a cord assembly with improperly connected terminals.
When a cord connector is wet, hazardous leakage can occur to the equipment grounding conductor and to humans who pick up that connector if they also provide a path to ground. Such leakage is not limited to the face of the connector but also develops at any wetted portion of it.

Guidelines for the Acceptable Use of Flexible Cords

Use examples include:

• Elevator cables
• Wiring of cranes and hoists
• Prevention of noise or vibration transmission
• Appliances where the fastening means and mechanical connections are designed to permit removal for maintenance and/or repair.

DO NOT use flexible wiring where frequent inspection is impractical or where damage is likely.
DO NOT run flexible cord through holes in walls, ceilings, floors, doorways, windows or hidden areas like conduits or other raceways.

The Most Common OSHA Electrical Violation

Improper grounding of circuitry and equipment is the most frequent violation of OSHA electrical regulations!
If a system with metal parts isn’t grounded correctly, those parts may become energized and create a serious hazard. Metal parts of appliances or other electronics that are connected to improperly grounded circuits also can become energized, and thus a shock hazard.
Grounded electrical systems are usually connected to a grounding rod placed approximately 6 feet into the earth.
Extension cords with broken wires or plugs may not provide a reliable path to ground. Still another consideration is that electrical systems may be grounded to water pipes, which provide a continuous path to ground when they are made of conductive materials (such as any number of types of metal). However, in renovations and repairs where parts of metal plumbing have been replaced with plastic pipe, the path to ground is interrupted and the result can be electrocutions and fires.

That’s It… You’re Grounded!

To ensure proper grounding, there are a number of simple controls that will help ensure a safer working environment.
Four components comprise a typical extension cord grounding system:

• A third wire in the plug, called a ground wire;
• A three-pronged plug with a grounding prong on one end of the cord;
• A three-wire, grounding-type receptacle at the other end of the cord;
• A properly grounded outlet

The OSHA standard requires the following two types of grounds:
A service (or system) ground consists of one white or gray grounded wire (the neutral, or grounded, conductor), which is grounded at the generator and at the service entrance of the building. A service ground generally protects machines, tools and insulation.
An equipment ground furnishes yet another path from equipment (tools or machines) to ground for enhanced worker protection. This type of ground provides additional protection for workers if a malfunction causes the metal parts of a device to become energized.
The only real downside to grounding is that a break in the system can occur without anyone knowing until someone gets a shock, since the break might not be visible to the eye. A device called a ground-fault circuit interrupter (GFCI) – referenced in standard 1926.404(b)(1)(i) – is one way to have backup protection in the event of a ground fault.

GFCIs – Way Better Than Having to Call a Whole Lifesaving Emergency Team!

A ground-fault circuit interrupter (GFCI) protects workers from shock by matching the amount of current going into an electrical device against the amount returning from the device.
Put another way, a GFCI is a fast-acting circuit breaker that can sense small imbalances in the circuit and immediately shut off the flow of electricity.
The use of these relatively simple, small devices has radically changed the safety of electrical systems for the better by interrupting electric power in as little as 1/40th of a second when the amount of current going out differs from the amount returning by as little as 5mA.
The National Electrical Code (NEC) requires that GFCIs be used when:

• Electricity is used near water (a common example is a hair dryer, which are now required to have GFCIs lest they fall [or be “accidentally” dropped] into a bathtub or sink…)
• Temporary wiring or extension cords are being used
• Circuits are providing power to outdoor receptacles or portable tools

While GFCIs successfully reduce electrical hazards on construction sites, they do not eliminate them. We will go into more depth on GFCIs later in the course.

Assured Equipment Grounding Conductor Program (AEGCP)

AEGCPs are implemented on construction sites to oversee line-to-line connections (which GFCIs cannot cover) as well as all cord sets, receptacles that are not part of a building or structure, and equipment connected by plug and cord.
Minimum requirements for the proper maintenance of an Assured Equipment Grounding Conductor Program include:

• Competent person to implement program
• Daily visual inspections
• Periodic test inspections (3 mos max for temporary or exposed cords; 6 mos for fixed, unexposed cords)
• Written description
• Record results of periodic tests

We will go into more depth on this later in the course.

Overloaded Circuits

Hazards can result when too many devices are plugged into a circuit. Wires can become overheated, which can cause a fire. Damaged tools that overheat can also cause a hazard, as can lack of overcurrent protection and insufficient wire insulation. Wire insulation can melt, which can cause arcing and a fire where the overload exists – even within a wall.
To prevent too much current in a circuit, circuit breakers or fuses are employed. Both circuit breakers and fuses serve the same purpose: They open a circuit that has become overloaded to shut off the electrical current, preventing damage from spreading throughout the whole system.
If a fuse blows, it is destroyed and must be replaced – as it is designed to be a “weak link” in the system that will melt when it is overloaded, thus containing the damage of the overload.
A circuit breaker serves the same purpose, but has contacts that are designed to open when the circuit becomes overloaded. The circuit can be reset by re-closing the contacts.
While both circuit breakers and fuses may help reduce the probability of a shock to your system, they are designed primarily to protect equipment and an operation’s electrical system. The only device designed specifically to protect people is a GFCI.

General Planning & Controls

Common Reasons for OSHA Electrical Violations

Part of the reason the OSHA electrical standard is necessary is that some employers – and workers – will opt to take the easy way out to get something done quickly instead of ensuring their safety and the safety of others by implementing the proper safeguards.
The misuse of equipment can translate into an OSHA violation and a hefty fine, not to mention accidents and injuries. Some of the most common scenarios of equipment misuse are as follows:

• Using multi-receptacle boxes that are designed to be securely mounted as “portable” stations by fitting them with a power cord and putting them on the floor
• Using equipment outside that is specifically labeled for use in dry, indoor locations only.
• Attaching ungrounded two-prong adapter plugs to three-prong cords and tools
• Using circuit breakers on fuses with the wrong rating for overcurrent protection
• Using cord or tools that have been modified from the way they were manufactured and/or meant to be used – for example, removing a face plate, insulation, or ground prongs
• Using cords or tools with exposed wires, and fraying, cut or worn insulation

Some relatively simple, common sense controls, a bit of knowledge and a lot of awareness can help ensure that the situations described in the list do not occur. We’ll review some of the categories in which construction workers have to be particularly aware.

What Should Be Done to Stay Safe

Use the three-stage safety model: (1) recognize, (2) evaluate, and (3) 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.
Step 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 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.

Step 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.

Step 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.

Power Tools

The following general precautions are among the more important safeguards that should be observed by those using electrical power tools:

• Never carry a tool by the cord or hose
• Never yank the cord or the hose to disconnect it from the receptacle
• Keep cords and hoses away from heat, oil, and sharp edges
• Disconnect tools when not in use, before servicing, and when changing accessories such as blades, bits and cutters
• All observers should be kept at a safe distance away from the work area
• Secure work with clamps or a vise, freeing both hands to operate the tool
• Avoid accidental starting. The worker should not hold a finger on the switch button while carrying a plugged-in tool.
• All portable electric tools that are damaged shall be removed from use and tagged “Do Not Use.”

Workers who use electric tools must guard against a number of hazards, the most serious being the possibility of electrocution. It is worth repeating that among the chief hazards of electric-powered tools are burns (particularly to the hands) and slight shocks that can cause injuries or even heart failure.
Even a low-voltage shock can cause heart fibrillation and even death, particularly if the shock is prolonged (since power tools tend to be tightly gripped, the duration of the shock is often longer than it might be with objects that are touched accidentally. And remember, even a tiny shock can surprise a worker, causing those on ladders or other elevated work surfaces (scaffolds, roofs) to pull back and lose their balance.
To protect the user from shock, tools must be equipped with either a three-wire cord with ground and be grounded, be double insulated, or be powered by a low-voltage isolation transformer.
Сurrents as low as 10 mA can freeze muscles, rendering someone unable to release the tool. Keep in mind that a tool like a power drill carries 30 times the amount of current required to kill a person!
Anytime an adapter is used to accommodate a two-hole receptacle, the adapter wire must be attached to a known ground. The third prong should never be removed from the plug. Double insulation is more convenient. The user and the tools are protected in two ways: by normal insulation on the wires inside, and by a housing that cannot conduct electricity to the operator in the event of a malfunction.
Some of the important general practices that should be followed when using electric tools include:

• Electric tools should be operated within their design limitations.
• Gloves and safety footwear are recommended during use of electric tools.
• When not in use, tools should be stored in a dry place.
• Electric tools should not be used in damp or wet locations.
• Work areas should be well lighted.

All hazards involved in the use of power tools can be prevented by following five basic safety rules:

1. Keep all tools in good condition with regular maintenance
2. Use the right tool for the job
3. Examine each tool for damage before use
4. Operate according to the manufacturer’s instructions
5. Provide and use the proper protective equipment

Temporary Lighting

Temporary lighting should be protected from damage and from contact with workers, and should not be suspended by cords unless designed to do so.
If flexible cords are used to supply temporary lighting, the cords must be approved for hard usage; for example, types “S, SO, ST and STO.”

Grounding And Insulation Preventive Measures

We have already touched upon grounding and insulation as controls for improper grounding of circuitry and equipment, and the use of GFCIs has been briefly mentioned.
However, ground-fault protection on construction sites is important enough to warrant reviewing some OSHA ground rules:

OSHA ground-fault protection rules and regulations have been determined necessary and appropriate for employee safety and health. Therefore, it is the employer’s responsibility to provide either: (a) ground-fault circuit interrupters on construction sites for receptacle outlets in use and not part of the permanent wiring of the building or structure; or (b) a scheduled and recorded assured equipment grounding conductor program on construction sites, covering all cord sets, receptacles which are not part of the permanent wiring of the building or structure, and equipment connected by cord and plug which are available for use or used by employees.

If ground-fault circuit interrupters are the protective means chosen, OSHA requirements read as follows:

The employer is required to provide approved ground-fault circuit interrupters for all 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites which are not a part of the permanent wiring of the building or structure and which are in use by employees. Receptacles on the ends of extension cords are not part of the permanent wiring and, therefore, must be protected by GFCIs whether or not the extension cord is plugged into permanent wiring.

These GFCIs monitor the current-to-the-load for leakage to ground. When this leakage exceeds 5 mA ± 1 mA, the GFCI interrupts the current. They are rated to trip quickly enough to prevent electrocution. This protection is required in addition to, not as a substitute for, the grounding requirements of OSHA safety and health rules and regulations, 29 CFR 1926. The requirements which employers must meet, if they choose the GFCI option, are stated in 29 CFR 1926.404(b)(1)(ii).

(ii) Ground-fault circuit interrupters. All 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have approved ground-fault circuit interrupters for personnel protection. Receptacles on a two-wire, single-phase portable or vehicle-mounted generator rated not more than 5kW, where the circuit conductors of the generator are insulated from the generator frame and all other grounded surfaces, need not be protected with ground-fault circuit interrupters.

If the employer chooses to implement an Assured Equipment Grounding Conductor Program (AEGCP), the actual OSHA guidelines are as follows:

The assured equipment grounding conductor program covers all cord sets, receptacles which are not a part of the permanent wiring of the building or structure, and equipment connected by cord and plug which are available for use or used by employees.

The rest of the requirements are stated in 29 CFR 1926.404(b)(1)(iii), but employers may provide additional tests or procedures.
OSHA requires that a written description of the employer’s assured equipment grounding conductor program, including the specific procedures adopted, be kept at the jobsite. This program should outline the employer’s specific procedures for the required equipment inspections, tests, and test schedule.
The required tests must be recorded, and the record maintained until replaced by a more current record. The written program description and the recorded tests must be made available, at the jobsite, to OSHA and to any affected employee upon request. The employer is required to designate one or more competent persons to implement the program.
NOTE: Electrical equipment noted in the assured equipment grounding conductor program must be visually inspected for damage or defects before each day’s use. Any damaged or defective equipment must not be used by the employee until repaired.
Two tests are required by OSHA. One is a continuity test to ensure that the equipment grounding conductor is electrically continuous. It must be performed on all cord sets, receptacles which are not part of the permanent wiring of the building or structure, and on cord- and plug-connected equipment which is required to be grounded. This test may be performed using a simple continuity tester, such as a lamp and battery, a bell and battery, an ohmmeter, or a receptacle tester.
The other test must be performed on receptacles and plugs to ensure that the equipment grounding conductor is connected to its proper terminal. This test can be performed with the same equipment used in the first test.
NOTE: These tests are required before first use, after any repairs, after damage is suspected to have occurred, and at 3-month intervals. Cord sets and receptacles which are essentially fixed and not exposed to damage must be tested at regular intervals not to exceed 6 months. Any equipment which fails to pass the required tests shall not be made available or used by employees.

How OSHA Instituted Its Plans for Dealing with Hazards

As mentioned much earlier in the course, when OSHA needed help in 1970 devising standards to keep workers safe from the myriad of electrical hazards, it noted that experts in electrical safety turned to the National Electrical Code (NEC). OSHA recognized the important role of the NEC by co-opting the entire 1971 NEC by reference into Subpart K of 29 Code of Federal Regulations Part 1926 (Construction Safety and Health Standards).
To review, Subpart K is divided into four major groups:

• Installation Safety Requirements
• Safety-Related Work Practices
• Safety-Related Maintenance and Environmental Considerations
• Safety Requirements for Special Equipment

We will address each of these separately.

Installation Safety Requirements

Following are steps the employer must take to ensure the safety of electrical equipment…but obviously, these same checkpoints can serve as a common-sense guide for employees! Review the lists below and double-check that the requirements are met. While the lists are by no means complete, it can’t hurt to read them – and it may save your life.
The safety of equipment must be determined by the following:

• Suitability for installation and use in conformity with the provisions of the standard – that is, suitability of equipment for an identified purpose evidenced by a listing, by labeling, or by certification for that identified purpose.
• Mechanical strength and durability. For parts designed to enclose and protect other equipment, this includes the adequacy of the protection thus provided.
• Electrical insulation
• Heating effects under conditions of use – if it starts to overheat disconnect it!
• Arcing effects
• Classification by type, size, voltage, current capacity, and specific use

Live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact.
Guarding of live parts must be accomplished as follows:

• Location in a cabinet, room, vault, or similar enclosure accessible only to qualified persons.
• Use of permanent, substantial partitions or screens to exclude unqualified persons.
• Location on a suitable balcony, gallery, or platform elevated and arranged to exclude unqualified persons.
• Elevation of eight feet or more above the floor.

Entrance to rooms and other guarded locations containing exposed live parts must be marked with conspicuous warning signs forbidding unqualified persons to enter.
For overcurrent protection of circuits rated 600 volts, nominal, or less.

• Conductors and equipment must be protected from overcurrent in accordance with their ability to safely conduct current and the conductors must have sufficient current-carrying capacity to carry the load.
• Overcurrent devices must not interrupt the continuity of the grounded conductor unless all conductors of the circuit are opened simultaneously, except for motor-running overload protection.
• Overcurrent devices must be readily accessible and not located where they could create an employee safety hazard by being exposed to physical damage or located in the vicinity of easily ignitable material.
• Fuses and circuit breakers must be so located or shielded that employees will not be burned or otherwise injured by their operation, e.g., arcing.

Safety-Related Work Requirements

An employer must not allow an employee to work near any part of an electric power circuit that the employee could contact in the course of work, unless the employee is protected against shock. This means the circuit must be deenergized and grounded or otherwise guarded by insulation or other means.
Even before work is begun, the employer must determine where any part of an exposed or concealed energized electric power circuit is located. This is necessary because a person, tool or machine could come into physical or electrical contact with the electric power circuit. The employer is required to advise employees using jack hammers, underground drilling equipment or hand tools that may contact a line must be provided with insulated protective gloves or insulated protective boots if required by a manufacture.

Lockout and Tagging of Circuits

Reference 1926.417 breaks this requirement down into four simple points:

• Controls. Controls that are to be deactivated during the course of work on energized or de-energized equipment or circuits shall be tagged.
• Equipment and circuits. Equipment or circuits that are deenergized must be rendered inoperative and have tags attached at all points where such equipment or circuits can be energized.
• Tags. Tags shall be placed to identify plainly the equipment or circuits being worked on.
• Lockout and Tagging. While any employee is exposed to contact with parts of electric equipment or circuits which have been de-energized, the circuits energizing the parts shall be locked out or tagged out or both.

Passageways and Open Spaces

Employer must provide barriers or other means of guarding to ensure that workspaces for electrical equipment are not used as passageways when energized parts of electrical equipment are exposed.
Work should be preplanned, hazard warnings should be posted near electrical equipment, and walkways and similar working spaces should be kept clear of electric cords.

Energized Parts & Equipment

Only qualified persons may work on electric circuit parts or equipment that has not been de-energized. Those people must be specially trained to be familiar with the proper use of special precautionary techniques, PPE, insulating and shielding materials, and insulated tools.
As mentioned, any live parts an employee might come in contact with must be de-energized before the employee works near or on them, unless the employer can show that de-energizing would actually introduce a greater (or additional) hazard or that it is infeasible because of operating limitations or the equipment design.
When exposed live parts are not de-energized, other safety precautions must be taken to protect employees.

Maintenance of Equipment

The employer must ensure that all wiring components and utilization equipment in hazardous locations are maintained in a dust-tight, dust-ignition-proof, or explosion-proof condition without loose or missing screws, gaskets, threaded connections, seals, or other impairments to a tight condition.

Environmental Deterioration of Equipment

Unless identified for use in the operating environment, no conductors or equipment can be located:

• In damp or wet locations.
• Where exposed to gases, fumes, vapors, liquids, or other agents having a deteriorating effect on the conductors or equipment.
• Where exposed to excessive temperatures.

Conclusion

Any time you are working with or around electricity, there are a series of hazards that can cause injury. To this end, your employer and OSHA have certain responsibilities to carry out and must implement certain controls to help prevent accidents. However, nothing will take the place of your own awareness… be sure to wear the proper PPE, use good work practices, and stay alert!