Know how to identify, recognize electrical and unapparent hazards

The purpose of this article is to help identify a variety of workplace hazards and provide basic electrical safety

By William McGugan and Tyler Roschen June 13, 2024


Learning Objectives

  • Identify electrical, weather-related and environmental-related hazards.
  • Recognize protection boundaries and a basic overview of electrically safe work conditions.
  • Understand basic electrical safety codes and resources for identifying other hazards.


Electrical safety insights

  • This article will briefly discuss some of the major electrical safety topics and will also cover other — sometimes so obvious as to become forgotten — hazards that workers may find themselves exposed to in the course of their work.
  • References and tools to help assist with electrical safety best practices include codes, standards, U.S. government websites and a variety of other resources.

Electrical safety topics include shock hazards, arc hazards and safe working conditions. Other hazards persist for those working with electrical systems, some of which are so obvious as to become forgotten.

The authors of this article strongly encourage all involved in electrical work, even tangentially, to familiarize themselves with the requirements of Occupational Health and Safety Administration (OSHA), NFPA 70E: Standard for Electrical Safety in the Workplace, NFPA 70: National Electrical Code, the National Electrical Safety Code (NESC), other industry consensus standards on safety and their company’s safety materials.

Electrical hazards

An electrical hazard is defined as a condition where there is the potential for injury from electric shock, arc flash burn, thermal burn or arc blast energy due to making direct or indirect contact with energized equipment or conductors. These hazards can expose workers to serious potential injuries and they should be aware and identify these hazards when near these types of equipment.

There are three major categories associated with electrical hazards in accordance with Annex K in NFPA 70E:

  • Electric shock.

  • Arc flash.

  • Arc blast.

Electric shock: Electric shock is associated with current passing through the body caused by contact or close approach to energized electrical conductors or circuit parts. Shock hazards exist when in contact with equipment or sources 50 Volts (V) or greater. An electric shock risk assessment is conducted to identify the voltage, limited approach and restricted approach boundaries and personal protective equipment (PPE) required to protect against electric shock hazards.

Figure 1: An example of a motor control center with lockout/tagout devices. Courtesy: CDM Smith

Figure 1: An example of a motor control center with lockout/tagout devices. Courtesy: CDM Smith

There are two electric shock protection boundaries that should be identified for each given piece of equipment: limited approach and restricted approach. These boundaries identify the distance, determined based on the voltage potential between the source and ground, from where qualified and unqualified persons, as defined by OSHA 29 and NFPA 70E, may interact with equipment where shock hazards are present.

  • Limited approach boundary: An unqualified person may enter this boundary under supervision of qualified persons.

  • Restricted approach boundary: Only qualified persons may enter this boundary with proper PPE as listed in NFPA 70E.

Arc flash: Arc flash is a release of thermal energy from an electric arc between electrical conductors or to ground. The amount of energy, or arc flash, is dependent on the fault current and clearing time. The fault current value is dependent on the utility and its equipment supply. The clearing time is the amount of time the overcurrent protective device takes to trip (open) during a fault situation. An arc flash risk assessment is conducted to identify the incident energy at the work distance (or arc flash PPE category), arc flash boundary and PPE required to protect against arc flash hazards.

Like the electric shock boundaries, although completely independent from one another, there is a single arc flash boundary required to be identified to determine the distance at which the incident energy equals 1.2 cal/cm2.

This value was determined based on the Stoll skin burn injury model, where the onset of a second-degree burn on unprotected skin is likely to occur at an exposure of 1.2 cal/ cm2 for one second. This value is deemed to be a curable burn.

Figure 2: This photo displays cold-related hazards due to ice forming in the working space of the cabinets. Courtesy: CDM Smith

Figure 2: This photo displays cold-related hazards due to ice forming in the working space of the cabinets. Courtesy: CDM Smith

When working within the arc flash boundary, proper clothing and PPE should be selected and worn for protection from arc flash hazards. Selection of proper PPE is determined based on either the incident energy method or the arc flash PPE category method as defined in NFPA 70E.

For example, when using the incident energy level method, NFPA 70E Table 130.5(G) should be used to select proper PPE based on amount of incident energy calculated for each individual equipment. When using the arc flash PPE category method, NFPA 70E Table 130.7(C)(15)(c) would be used for selecting proper PPE. Outside of this boundary, PPE is not required. However, caution should still be considered as injury can still occur even when working outside of the arc flash boundary.

Arc blast: Arc blast is simultaneous with an arc flash and is the pressure wave released during an arc flash event. An arc blast, traditionally associated with an incident energy level of 40 cal/cm2, can throw people and objects due to this pressure wave. However, NFPA 70E no longer defines this 40 cal/cm2 limit. PPE can be rated above 40 cal/cm2, but at these levels the actual blast will be more potentially lethal. There is currently no assessment or method per NFPA 70E to help identify proper PPE to prevent injuries due to an arc blast.

There are other important aspects to electrical safety regarding these electrical hazards, including establishing electrically safe work conditions. An electrically safe work condition as defined by NFPA 70E is “a state in which an electrical conductor or circuit part has been disconnected from energized parts, locked/tagged in accordance with established standards, tested for the absence of voltage and, if necessary, temporarily grounded for personnel protection.” Establishing this electrically safe work condition is employed to prevent injury from either direct or indirect electrical contact.

The process for establishing and verifying an electrically safe condition is based on NFPA 70E and includes eight items:

  • Determine all possible electrical sources.

  • Open disconnecting devices(s) for each source.

  • Visually verify that all blades of disconnecting devices are withdrawn to the test or full disconnected position.

  • Release stored electrical energy.

  • Block or relieve stored nonelectrical energy in devices.

  • Apply lockout/tagout devices.

  • Use adequately rated portable test instrument to test conductors for absence of voltage.

  • Where the possibility of induced voltages or stored electrical energy exists, ground all circuit conductors and circuit parts before touching them.

Overall, it is vital for worker’s safety to be aware of electrical hazards and how to properly prepare to work on or near energized or unenergized equipment. Other important subjects, such as equipment maintenance and proper training, also exist to help prevent electrical hazards but are not discussed in this article.

Whether working on energized or unenergized equipment, it is important to maintain an electrically safe work condition, identify and wear proper PPE to help prevent against injury to electrical hazards. Other unapparent hazards that workers may encounter are as important as the electrical hazards already discussed.

Weather-related hazards

Weather-related hazards for people working on or around electrical equipment are most common at temperature extremes, such as when it is hot, humid, cold or windy. During hot and/or humid conditions, major risks include dehydration, heat exhaustion, heat stroke and somewhat ironically, overhydration. During cold conditions, major risks include hypothermia and frostbite. As weather-related hazards can dull mental and physical acuity, they can be especially concerning when working around electrical equipment.

Heat-related hazards: Heat exhaustion occurs when a person’s body loses excessive amounts of water and salt. Symptoms include headache, nausea, dizziness, thirst and heavy sweating. Heat stroke occurs when a person’s body can no longer control its temperature and can cause permanent damage or death. Symptoms include confusion, loss of consciousness, profuse sweating, seizures and very high body temperatures.

First aid includes getting medical treatment, removing the person from the heat, ensuring the person drinks liquids, removing unnecessary clothing and applying cold compresses. For heat stroke, immediate emergency medical attention is necessary and more drastic methods to cool the affected person are encouraged, including ice baths.

Figure 3: An example of a natural hazard where a snake was hiding in an electrical enclosure. Courtesy: CDM Smith

Figure 3: An example of a natural hazard where a snake was hiding in an electrical enclosure. Courtesy: CDM Smith

Dehydration and overhydration (or water intoxication) can have similar symptoms — both commonly presenting with nausea, fatigue and headaches — making communication key in understanding what first aid efforts should be undertaken. While the treatment for dehydration is relatively straightforward, cool down and hydrate, overhydration may require medical attention.

Cold-related hazards: Hypothermia occurs when a person’s body loses heat faster than it can make it, leading to low body temperatures, which can in turn affect a person’s decision making and physical movement. Shivering, fatigue, loss of coordination and confusion indicate early stages of hypothermia. A lack of shivering can indicate late stages of hypothermia, along with blue skin, dilated pupils, slow breathing and loss of consciousness. First aid includes moving the person to a warm area, removing wet clothing, warming their body — torso and head first and providing warm nonalcoholic drinks.

Environmental hazards: Chemicals, toxins and other exposures

Many other health hazards that may be encountered by electrical personnel are from chemicals or other compounds that have served or continue to serve an important purpose in the electrical industry but are also now known to cause cancer or other serious diseases. Examples include polychlorinated biphenyls (PCBs), asbestos and sulfur hexafluoride (SF6) byproducts. Workers should also be cognizant of other chemicals and exposure hazards in the areas they are working, for instance, caustic chemicals in an industrial plant, microorganisms in a wastewater treatment facility, or other natural hazards such as snakes or poison ivy.

Polychlorinated biphenyls: PCBs are synthetic chemicals which were used in transformers, fluorescent lighting and other electrical equipment in the United States until 1977. PCBs were excellent electrical insulators but can cause severe skin and eye irritation in workers that breathe contaminated air or touch contaminated surfaces.

While most of this equipment is at or beyond its expected service life, PCB-contaminated equipment or areas may still be encountered. Given such equipment’s age and likely need for maintenance, it is more likely to leak contaminated oil. Federal law requires PCB-contaminated equipment to be marked with an appropriate hazard label. Labels are required to indicate insulating fluids are non-PCB. Assume equipment contains PCBs unless labeled otherwise.

Asbestos: For similar reasons to PCBs, asbestos was used for decades in the electrical industry (and industry at large) due to its excellent heat and electrical insulation characteristics. Banned in 1989 due to its association with mesothelioma and other cancers, asbestos may still be found in many electrical installations, especially in circuit breaker arc chutes. Asbestos may also be found in wire insulation or asbestos-cement conduits. In general, asbestos is only a health threat to humans if its fibers are inhaled.

Sulfur hexafluoride byproducts: SF6 gas is used as an electrical and mechanical insulating material in medium- and high-voltage electrical equipment. SF6 gas itself is not a significant direct health risk to humans, though it is the most potent greenhouse gas according to the Environmental Protection Agency and can greatly impact global climate change.

Byproducts of SF6 gas — which are created when high fault currents or other electrical discharges pass through the gas — can be toxic to humans, often causing irritation or even severe burns to the eyes and the respiratory system. While many SF6 byproducts appear as light-colored powder with strong sulfur smells, the most potently toxic byproduct is odorless.

Figure 4: A diagram displaying the restricted, limited and arc flash boundaries. Courtesy: CDM Smith

Figure 4: A diagram displaying the restricted, limited and arc flash boundaries. Courtesy: CDM Smith

Natural hazards: Electrical workers are likely to be exposed to smaller creatures such as snakes, spiders, bees, ants and ticks. While most such creatures are harmless to humans, there are varieties that are venomous or otherwise potentially dangerous. Electrical equipment offers spiders, bees and other flying biting/stinging insects, ants and even snakes warm, sheltered locations in which to rest or build a home. Snakes, spiders or ticks may be encountered when accessing outdoor equipment in areas that have not been well maintained in places like overgrown grass or shrubbery. In general, such animals are unlikely to bother workers unless disturbed or directly confronted, so a worker may reduce their exposure simply by being aware of their surroundings and avoiding interactions.

When bitten by a spider or snake, common incorrect actions include trying to catch or handle the creature, even when dead (instead: take a picture), attempting to suck out the poison, applying tourniquets, etc. First aid for most incidents includes washing the bite with soap and water, removing rings and watches before swelling occurs and seeking immediate medical attention.

Ticks should be removed within 24 to 48 hours using clean, precision tweezers to carefully grip the tick as near to the skin’s surface as feasible. Pull upward with steady, even pressure, being sure that no parts of the head remain, per the CDC.

By adhering to these many guidelines, electrical safety practices in the workplace can be improved.

Author Bio: William McGugan is an electrical engineer at CDM Smith with a focus on the design and analysis of electrical power systems. Tyler Roschen is an electrical engineer at CDM Smith with expertise in electrical design with a focus on power concepts.