How Electricity Acts | OSHA

Electricity is essential to modern life, both at home and on the job. Some employees work with electricity directly, as is the case with engineers, electricians, electronic technicians, and power line workers. Others, such as office workers and sales people, work with it indirectly. As a source of power, electricity is accepted without much thought to the hazards encountered. Perhaps because it has become such a familiar part of our surroundings, it often is not treated with the respect it deserves.

To handle electricity safely, it is necessary to understand how it acts, how it can be directed, what hazards it presents, and how these hazards can be controlled. Operating an electric switch may be considered analogous to turning on a water faucet. Behind the faucet or switch there must be a source of water or electricity, with something to transport it, and with pressure to make it flow. In the case of water, the source is a reservoir or pumping station; the transportation is through pipes; and the force to make it flow is pressure, provided by a pump. For electricity, the source is the power generating station; current travels through electric conductors in the form of wires; and pressure, measured in volts, is provided by a generator.

Resistance to the flow of electricity is measured in ohms and varies widely. It is determined by three factors:
  • Nature of the substance itself,
  • Length and cross-sectional area (size) of the substance, and
  • Temperature of the substance.
Some substances, such as metals, offer very little resistance to the flow of electric current and are called conductors. Other substances, such as bakelite, porcelain, pottery, and dry wood, offer such a high resistance that they can be used to prevent the flow of electric current and are called insulators.

Dry wood has a high resistance, but when saturated with water its resistance drops to the point where it will readily conduct electricity. The same thing is true of human skin.

When it is dry, skin has a fairly high resistance to electric current; but when it is moist, there is a radical drop in resistance. Pure water is a poor conductor, but small amounts of impurities, such as salt and acid (both of which are contained in perspiration), make it a ready conductor. When water is present either in the environment or on the skin, anyone working with electricity should exercise even more caution than they normally would.

OSHA's Electrical Standards

OSHA's general industry electrical standards, found in Subpart S, §1910.301 through §1910.399 are based on the National Fire Protection Association's Standard NFPA 70E,Electrical Safety Requirements for Employee Workplaces, and the National Electrical Code (NEC). In addition to general industry, they apply to shipyard employment, longshoring, and marine terminals.

OSHA also has electrical standards for construction, but recommends that employers in this industry follow the general industry electrical standards whenever possible for hazards that are not addressed by their industryspecific standards.

The electrical standards help minimize potential electric-related hazards by specifying safety aspects in the design and use of electrical equipment and systems. Currently, the standards cover only those parts of any electrical system that an employee would normally use or contact. For example, the exposed and/or operating elements of an electrical installation — lighting, equipment, motors, machines, appliances, switches, controls, and enclosures — must be constructed and installed so as to minimize workplace electrical dangers.

OSHA Revises Design and Installation Requirements

On February 14, 2007, OSHA issued a revised standard for the design and installation of electric equipment. It is the first revision to the electrical installation requirements since 1981. The changes reflect current industry practices by drawing heavily from the 2000 edition of the National Fire Protection Association's (NFPA) Electrical Safety Requirements for Employee Workplaces (NFPA 70E), and the 2002 edition of the National Electrical Code (NEC).

 The revised provisions, which were effective August 13, 2007, are intended to help eliminate inconsistencies and confusion between OSHA's requirements and many state and local building codes which have adopted updated NFPA and NEC provisions. They also address stakeholder requests to revise the standard so that it conforms with the most recent edition of NFPA 70E with requirements for:
  • Identifying multi-wire branch circuits;
  • Providing signage for on-site emergency power sources; and
  • Marking and listing power sources for power-limited fire alarm circuit power sources.
For workplaces covered by the changes, the impact is far-reaching. "Qualified" employees have new "workmanship" requirements and new rules for replacing equipment. "Unqualified" employees (such as safety supervisors) have new requirements for locking out and tagging disconnecting means for certain electrical equipment.
Qualified versus Unqualified Workers
For some time, OSHA has divided employees into two groups regarding the training and experience levels needed to work on electrical systems. OSHA uses the term "qualified" and "unqualified" to distinguish between those employees.

The qualified person must know when, where, and how to place barriers; how to lockout and tag a disconnecting means; and how to work on the system. Some new requirements specifically for qualified employees address:
  • Workmanship when installing electrical equipment such as rat's nest and wiring packed too tight (fire hazard).
  • Working space around electrical equipment (elbow room).
  • Procedures for replacing electrical equipment such as new receptacles.
Unqualified employees, those that do not work directly with electrical systems, still have to be able to recognize electrical hazards, stay clear of barricaded areas when qualified employees are working on electrical systems, and recognize appropriate lockout/tagout implementation. Additionally, they have to ensure that portable tools and extension cords are plugged into Ground Fault Circuit Interrupters (GFCIs) and that equipment with flexible cords (i.e., the cords that came with the equipment) are plugged directly into a receptacle.

The following section provides an overview of basic electrical safety for individuals with little or limited training or familiarity with electrical hazards. The concepts and principles presented will help further an understanding of OSHA's electrical safety standards.

Hot Topics: Lockout/Tagout and Machine Guarding

Hazard of Unexpected Energization

The Lockout/Tagout standard does not apply to servicing and maintenance operations if employees are not exposed to the risk of injury from the unexpected energization, start up, or release of hazardous energy while performing service or maintenance tasks.

Some servicing or maintenance activities do not expose workers to potential harm from the unexpected energization, startup, or release of hazardous energy because precautions taken by the employer provide effective employee protection when performing servicing and maintenance operations. These measures may include the use of a multi-step startup procedure, time delays, or audible warnings. In such relatively uncommon situations, lockout/tagout requirements do not apply. However, such alternative precautions must be carefully evaluated for their effectiveness in light of the configuration of the machinery, the reliability of the alternative measures, employee training, and other factors.

The Lockout/Tagout standard does not apply to servicing or maintaining cord- and plug-connected electrical equipment when the equipment is unplugged from its energy source and the plug is under the exclusive control of the employee performing the service and/or maintenance activity. "Under the exclusive control" refers to instances in which the plug is physically in the possession of the employee, or in arm's reach and in the line of sight of the employee, or in which the employee has affixed a lockout/tagout device to the plug. This enables the employee to prevent the equipment from becoming reenergized during servicing or maintenance.

Normal Production Operations vs. Servicing and/or Maintenance

The Lockout/Tagout standard makes a distinction between two types of workplace activities: servicing and/or maintenance and normal production operations. It is intended to provide employees with protection from the unexpected energization, start up, or release of stored energy, while performing servicing and/or maintenance operations. The machine guarding standards are intended to provide employee protection against the hazardous energy associated with normal production operations. However, certain types of servicing and/or maintenance performed during normal production operations are also subject to the Lockout/Tagout standard.

Under the Lockout/Tagout standard, normal production operations are defined as the utilization of a machine or equipment to perform its intended production function.

Normal production operation is the mode in which an energized machine or equipment operates to either manufacture a product or perform a function necessary to assist in the manufacturing process. This mode of operation may present additional hazards to employees, including points of operation; e.g. ingoing nip points, crushing hazards due to the motion of the machine or equipment and due to the movement of the power transmission apparatus. The machine guarding standards establish provisions for employee protection against hazardous energy and points of operation while the equipment is energized in order to perform its intended production function.

Employee protection from hazardous energy during normal production operations is generally accomplished by compliance with applicable machine guarding standards. However, if a servicing or maintenance operation takes place during normal production operations, and the employee is required to remove or bypass machine guarding required by Subpart O, or to place part of his/her body into an area in which he/she is exposed to the unexpected energization or activation of the equipment, the protections of the Lockout/Tagout standard would apply. In these circumstances, the employee performing servicing or maintenance would be subjected to hazards that are not encountered as part of the normal production operation.

Servicing and/or maintenance is defined as workplace activities, including installing, setting up, inspecting, adjusting, repairing, replacing, constructing, modifying, and maintaining and/or servicing machines or equipment. These activities include lubrication, cleaning or unjamming of machines or equipment, and making adjustments or tool changes, during which the employee may be exposed to the unexpected energization or startup of the equipment or release of hazardous energy. Setting up would include any work performed to prepare a machine or equipment to perform its normal production operation.

Many servicing and/or maintenance activities require the machine, equipment, or its components to be disassembled or dismantled. These tasks are typically performed with the equipment stopped. Other servicing and maintenance activities would not require the employer to disassemble or dismantle the machine or equipment but would nonetheless require shutdown of the equipment or machine. This would cause the associated production process to be discontinued during the servicing and maintenance.

Servicing and/or maintenance activities may expose an employee to the unexpected energization, start up, or release of stored energy. The Lockout/Tagout standard establishes provisions to deenergize equipment in such cases and to render all potentially hazardous energy safe, prior to engaging in servicing and maintenance activities. These provisions are intended to protect employees from the equipment being energized or started while servicing and/or maintenance is being performed.

Minor Servicing Exception

Some servicing operations performed during normal production operations are excepted from coverage under the Lockout/Tagout standard. This exception is referred to as the minor servicing exception. The Lockout/Tagout standard is not intended to cover minor servicing activities that are necessary to carry out the production process provided that associated danger zones are properly guarded. The machine guarding standards cover these types of operations.

The Lockout/Tagout standard contains specific criteria that must be met for the minor servicing exception to apply. Minor tool changes and adjustments,and other minor servicing activities that take place during normal production operations, are not covered by the standard if they are routine, repetitive, and integral to the use of the equipment for production, provided that the work is performed using alternative measures which provide effective protection.
If the servicing operation is routine, repetitive, and must be performed as part of the production process, the employer must use alternative protective methods or safeguarding devices (such as remote oilers and specially designed servicing tools), to protect employees.

Three specific criteria can be used to determine if the minor servicing exception would apply to a particular activity.
First, the activity must be conducted during normal production operations, i.e., while the machine or equipment is actually performing its intended production function.
Second, the activity must be:
  • Routine: The activity must be a regular course of procedure and be in accordance with established practices.
  • Repetitive: The activity must be regularly repeated as part of the production process.
  • Integral: The activity must be essential to the production process.
Third, if all of these apply, the employer must use alternative measures to provide effective protection from the hazardous energy. Some acceptable alternative measures include specially designed tools, remote devices, interlocked barrier guards, local disconnects, or control switches which are under the exclusive control of the employer performing the minor servicing. These alternative measures must enable the employee to safely perform the servicing task without being exposed to the unexpected energization or activation of the equipment, or the release of stored energy.

If the minor servicing exception is not met in full, the Lockout/Tagout standard is applicable and the machine or equipment must be deenergized and all potentially hazardous energy rendered safe.

Examples of Servicing and Maintenance vs. Normal Production Operations and Minor Servicing

Printing Shop
In a printing shop, when a printing press is being used to produce printed materials, there is often the need to make minor adjustments such as to correct for paper misalignment while the press is running. This is a part of the production process, and is subject to the machine guarding requirements. The use of remote control devices which keep the employees from reaching beyond the machine guards, or the use of inch (or jog) devices that permit machine speed control for test purposesobviate the need for lockout/tagout. However, printing presses may jam, requiring an employee to bypass the machine guards in order to reach the area of the jam and clear it. Although the need to unjam the machine arises during normal production operations, it is a servicing activity that involves employee exposure to unexpected activation of the machine or release of energy, and is covered under the Lockout/Tagout standard.
Machine Shop
In a machine shop, a milling machine operator must adjust the flow of coolant oil to parts being milled while the cutting tool is in operation. This operation, which is part of the normal production process for the machine, is covered by the machine guarding requirements, which prevent employee contact with nip points and other points of operation. However, if it becomes necessary to perform an adjustment which requires the employee to bypass a guard or to place any part of his/her body in an area where work is performed on the material or where a danger zone exists during the machine's operating cycle, the Lockout/Tagout standard applies. If this step is performed without having to bypass the guard, reach into a danger zone, or otherwise expose the employee to the potential release of energy or the unexpected activation of the machine, the Lockout/Tagout standard would not apply.
Plastic Sheet Application Machine
An employee is operating a machine that applies and seals a clear plastic sheet around a packaged product. There is a blade on the machine that cuts the plastic sheets, and this blade must be cleaned periodically during the production process. Since the process must be stopped to clean off the blade, that this operation is more in the nature of servicing or maintenance than normal production; on the other hand, since it must be performed frequently during production, it is arguable also part of the production process. Because the requirements of the Lockout/Tagout standard and Subpart O dovetail, protection must be provided regardless of whether the above operation is considered to be production or servicing. If it is considered by the employer to be production, the employee must be fully protected from the dangers of contacting the blade or other harmful machine parts; the cleaning must be done with special tools and procedures to provide the necessary protection. However, if it is considered to be servicing, outside of production, and the employee is exposed to a point of operation or an associated danger zone, the provisions of the Lockout/Tagout standard would apply.

Hot Topics: Multiple Energy Sources/Multiple Items of Equipment

Multiple Energy Sources

Equipment or machines that are subject to the Lockout/Tagout standard may possess more than one type of hazardous energy. These may be in the form of mechanical, hydraulic, pneumatic, chemical, thermal, or other types of energy. Any such hazardous energy sources must be locked out/tagged out and all stored energy dissipated and/or restrained before an authorized employee engages in any servicing and maintenance activity.

Hazardous Energy from Interconnected or Nearby Machines or Equipment

When authorized employees implement an energy control procedure for a particular machine or equipment without regard for other machines or equipment in the area, they could still be subject to hazardous energy from interconnected or nearby machines or equipment.

Interconnected Machines or Equipment

If an authorized employee is exposed to the unexpected energization, start up, or release of stored energy from interconnected machines or equipment, the energy control procedures for all interconnected machines or pieces of equipment must be implemented.

Example: An authorized employee is changing a snapped belt on a motor. The authorized employee has deenergized and locked out the motor according to the energy control procedure for that piece of equipment. The motor is located directly over the interconnected conveyor, which is stopped but has not been deenergized or locked out. The conveyor has a different energy isolation point than the motor and may have an auxiliary power source or the capacity to release stored energy and startup unexpectedly. The authorized employee must stand on the conveyor in order to replace the belt. If the conveyor were unexpectedly started, the authorized employee could be severely injured. Since the conveyor is interconnected and exposes the authorized employee to the potential for injury from unexpected startup, the energy control procedures for the motor must ensure that servicing and maintenance employees are not exposed to hazards posed by the conveyor. The energy control procedures for the motor must require that energy control procedures for the conveyor be implemented, as well.

Nearby Machines or Equipment

If an authorized employee, in performing service and maintenance work on a machine or piece of equipment, is exposed to hazardous energy from nearby machines or equipment, the employer is required to provide the employee with protection from these hazardous energy sources.

Example: Using the belt replacement scenario above, the authorized employee could be subject to the hazardous energy associated with a nearby production process where a robot arm is operating. When the robot arm operates, it could strike the authorized employee replacing the belt. In this event, the employer must provide protection from the hazardous energy associated with the nearby robot arm by either:
  • Complying with the machine safeguarding standards and effectively guarding the nearby robot arm to not only protect the operators of the equipment but to protect servicing and maintenance employees replacing the belt.
  • Locking out or tagging out the nearby robot arm if:
    • the guarding is not adequate, or
    • the design or installation of the equipment would not permit such machine safeguarding, or
    • compliance with the Lockout/Tagout standard, 1910.147, provides the only feasible method.
In either instance, the employer must ensure that servicing and maintenance employees are not subject to hazardous energy from nearby machinery and equipment while carrying out servicing and maintenance activities on machines or equipment.

Hot Topics: Group Lockout or Tagout

Group Lockout and Tagout Procedures

Whenever servicing and/or maintenance is performed by a group of employees, the employer must develop and implement an energy control procedure that provides authorized and affected employees with the same level of protection as a personal lockout or tagout device. The requirements for group lockout or tagout are set out in section 1910.147(f)(3).

Servicing and maintenance operations performed by a group of employees are often more complex than servicing or maintenance performed by an individual. As a result, group lockout or tagout operations typically require more coordination and communication than personal lockout or tagout operations. Greater coordination between employees is particularly important when more than one craft or department must be involved to complete the task.

Under the standard's group lockout/tagout requirements, a single authorized employee must assume the overall responsibility for the control of hazardous energy for all members of the group while the servicing or maintenance work is in progress.

The authorized employee with the overall responsibility must implement the energy control procedures, communicate the purpose of the operation to the servicing and maintenance employees, coordinate the operation, and ensure that all procedural steps have been properly completed. In such operations, it is critical that each authorized employee involved in the group lockout/tagout activity be familiar with the type and magnitude of energy that may be present during the servicing and maintenance work.

In addition, each employee must affix his/her personal lockout or tagout device to the group lockout device, group lockbox, or comparable mechanism, before engaging in the servicing and maintenance operation. This enables the authorized employee to have control over his/her own protection, and verify that the equipment has been properly deenergized. Additionally, the lockout or tagout device will inform other persons that the employee is working on the equipment, and as long as the device remains attached, the authorized person in charge of the group lockout or tagout knows that the work has not been completed and that it is not safe to reenergize the equipment.

The servicing employee will continue to be protected by his/her lockout or tagout device until it is removed. The authorized employee in charge of the group lockout or tagout must not remove the group lockout or tagout device until each employee in the group has removed his/her personal device, indicating that he/she is no longer exposed to the hazards from the servicing operation.

When the activities involving group lockout or tagout extend into another workshift, or there is a change of authorized employees, the provisions for shift or personnel changes must also be followed.

Work Authorization Permits

Work authorization permits may play a role in an employer's group lockout/tagout procedures. A work authorization permit is a document authorizing employees to perform specific tasks. While the Lockout/Tagout standard does not specifically require the use of a work authorization permit, these documents may be used as a means of achieving compliance with the group lockout or tagout requirements.

If a work authorization permit is used to achieve compliance with group lockout/tagout provisions, it must be included in the employer's written procedures. The permit must identify the equipment to be serviced, the types and unique energy characteristics to be encountered, methods for safe work, and the process or procedures to be used to accomplish the task.

Uncontrolled Hazardous Energy Case Studies

Workers may be exposed to hazardous energy in several forms and combinations during installation, maintenance, service, or repair work. A comprehensive hazardous energy control program should address all forms of hazardous energy:
  • Kinetic (mechanical) energy in the moving parts of mechanical systems.
  • Potential energy stored in pressure vessels, gas tanks, hydraulic or pneumatic systems, and springs (potential energy can be released as hazardous kinetic energy).
  • Electrical energy from generated electrical power, static sources, or electrical storage devices (such as batteries or capacitors).
  • Thermal energy (high or low temperature) resulting from mechanical work, radiation, chemical reaction, or electrical resistance.

Case Studies

Between 1982 and 1997, The National Institute for Occupational Safety and Health (NIOSH) investigated 152 fatal incidents in which workers contacted uncontrolled hazardous energy. The following case reports summarize five of these investigations.
1. Uncontrolled Kinetic Energy
A 25-year-old male worker at a concrete pipe manufacturing facility died from injuries he received while cleaning a ribbon-type concrete mixer. The victim's daily tasks included cleaning out the concrete mixer at the end of the shift. The clean-out procedure was to shut off the power at the breaker panel (approximately 35 feet from the mixer), push the toggle switch by the mixer to make sure that the power was off, and then enter the mixer to clean it.

No one witnessed the event, but investigators concluded that the mixer operator had shut off the main breaker and then made a telephone call instead of following the normal procedure for checking the mixer before anyone entered it. The victim did not know that the operator had de-energized the mixer at the breaker. Thinking he was turning the mixer off, he activated the breaker switch and energized the mixer. The victim then entered the mixer and began cleaning without first pushing the toggle switch to make sure that the equipment was deenergized. The mixer operator returned from making his telephone call and pushed the toggle switch to check that the mixer was deenergized. The mixer started, and the operator heard the victim scream. He went immediately to the main breaker panel and shut off the mixer.

Within 30 minutes, the emergency medical service (EMS) transported the victim to a local hospital and then to a local trauma center. He died approximately 4 hours later [NIOSH 1995].
2. Uncontrolled Electrical Energy
A 53-year-old journeyman wireman was electrocuted when he contacted two energized, 6.9-kilovolt buss terminals. The victim and two coworkers (all contract employees) were installing electrical components of a sulfur dioxide emission control system in a 14-compartment switch house.

The circuit breaker protecting the internal buss (a conducting bar, rod, or tube that carries heavy currents to supply several electric circuits) within the switch house had been tripped out and marked with a tag — but it had not been secured by locking. This procedure was consistent with the hazardous energy control procedures of the power plant.

The victim and his coworkers were wiping down the individual compartments before a pre-startup inspection by power plant personnel. Without the knowledge of the victim and his coworkers, power plant personnel had energized the internal buss in the switch house. When the victim began to wipe down one of the compartments at the south end of the switch house, he contacted the A-phase buss terminal with his right hand and the C-phase buss terminal with his left hand. This act completed a path between phases, and the victim was electrocuted.
A coworker walking past the victim during the incident was blown backward by the arcing and received first-degree flash burns on his face and neck. A second coworker at the north end of the switch house heard the explosion and came to help. He notified the contractor's safety coordinator by radio and requested EMS. The EMS responded in about 15 minutes and transported the victim to a local hospital emergency room where he was pronounced dead [NIOSH 1994].
3. Uncontrolled Kinetic Energy
A 38-year-old worker at a county sanitary landfill died after falling into a large trash compactor used to bale cardboard for recycling. The cardboard was lifted 20 feet by a belt conveyor and fed through a 20- by 44-inch opening into a hopper. The hopper had automatic controls that activated the baler when enough material collected in the baling chamber. When the baler was activated, material in the chamber was compressed by a ram that entered the chamber from the side. Excess material above the chamber was trimmed by a shearer.

On the day of the incident, cardboard jammed at the conveyor discharge opening. Without stopping, deenergizing, or locking out the equipment, the victim rode the conveyor up to the discharge opening to clear the jam. He fell into the hopper and the baling cycle was automatically activated, amputating his legs. The victim bled to death before he could be removed from the machine [Colorado Department of Public Health and Environment 1994].
4. Uncontrolled Potential Energy
The 32-year-old owner of a heavy equipment maintenance business died after a wheel and tire assembly exploded during repair work. The victim was removing the assembly from a test roller when it exploded and struck him with the flying split rim of the wheel.

The test roller was a large, two-wheeled cart that carried about 60,000 pounds of concrete weights. The roller was used in highway construction to test road surfaces for proper compaction.

The victim had been working as a subcontractor to repair the wheel and tire assembly, which had been smoking earlier in the day and was believed to be rubbing against the concrete weights. The assembly consisted of a two-piece outside rim and an inside ring retainer that was held together and mounted on the axle by 20 wheel bolts and nuts. Normal air pressure for the mounted tire was 70 psi.

The victim raised and blocked the roller. Without discharging the air from the tire and using no personal protective equipment, he began to remove the wheel nuts using a pneumatic impact wrench. He had no training or experience with this type of work or in the servicing of this type of wheel. He did not realize that only some of the bolts held the wheel tire assembly to the axle. The remainder held the outer half of the rim to the inside half, securing the tire to the wheel. As the victim removed the nineteenth wheel nut, the pressurized air in the tire discharged explosively, causing the split rim to fly off the wheel and strike him. He died from cerebral contusions and lacerations [Minnesota Department of Health 1992].
5. Uncontrolled Kinetic and Thermal Energy
A 33-year-old janitorial worker died after he was trapped inside a linen dryer at a hospital laundry while cleaning plastic debris from the inside of the dryer drum. The cleaning task (which usually took 15 minutes to an hour) involved propping open the door to the dryer with a piece of wood and entering the 4- by 8-foot dryer drum. The melted debris was removed by scraping and chiseling it with screwdrivers and chisels. The dryer was part of an automated system that delivered wet laundry from the washer through an overhead conveyor to the dryer, where it was dried during a 6-minute cycle with air temperatures of 217° to 230° F. The system control panel was equipped with an error light that was activated if the dryer door was open, indicating that the dryer was out of service.

On the night of the incident, the victim propped the door open and entered the dryer drum without deenergizing or locking out the dryer. He began to clean the inside of the drum. Although the error light had been activated when the door was propped open, the signal was misinterpreted by a coworker, who restarted the system. When the system was restarted, the overhead conveyor delivered a 200-pound load of wet laundryto the dryer — knocking out the wooden door prop, trapping the victim inside, and automatically starting the drying cycle. The victim remained trapped inside until the cycle was completed and was discovered when the load was discharged from the dryer. He died thirty minutes later of severe burns and blunt head trauma [Massachusetts Department of Public Health 1992].


Review of the NIOSH data indicates that three related factors contribute to injuries and deaths that occur when workers perform installation, maintenance, service, or repair work near hazardous energy sources:
  • Failure to completely deenergize, isolate, block, and/or dissipate the hazardous energy source.
  • Failure to lockout and tagout energy control devices and isolation points after the hazardous energy source has been deenergized.
  • Failure to verify that the hazardous energy source was deenergized before beginning work.
These fatalities could have been prevented if comprehensive hazardous energy control procedures had been implemented and followed.

NIOSH recommends that employers implement the following steps to prevent injuries and deaths of workers who must work with hazardous energy in their jobs:
  1. Comply with OSHA regulations.
  2. Develop and implement a hazardous energy control program.
  3. Identify and label all hazardous energy sources.
  4. Deenergize, isolate, block, and/or dissipate all forms of hazardous energy before work begins.
  5. Establish lockout/tagout programs that:
    • Require workers to secure energy control devices with their own individually assigned locks and keys — only one key for each lock the worker controls (Use of master keys should be reserved for unusual circumstances when the worker is absent from the workplace. However, if master keys are necessary, keep them under supervisory control. List the proper procedures for using them in the written program for controlling hazardous energy.);
    • Require that each lock used to secure an energy control device be clearly labeled with durable tags to identify the worker assigned to the lock;
    • Make sure that the worker who installs a lock is the one who removes it after all work has been completed; and
    • If work is not completed when the shift changes, workers arriving on shift should apply their locks before departing workers remove their locks.
  6. Verify by test and/or observation that all energy sources are deenergized before work begins.
  7. Inspect repair work before reactivating the equipment.
  8. Make sure that all workers are clear of danger points before reenergizing the system.
  9. Train all workers in the basic concepts of hazardous energy control.
  10. Include a hazardous energy control program with any confined space entry program.
  11. Encourage manufacturers to design machines and systems that make it easy to control hazardous energy.

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