Understand what arc flash is, its causes, and the dangers that it poses. Learn what you can do for arc flash prevention and the protection of workers in various sites and areas.
Published 30 Nov 2022
Creating an Electrically Safe Working Condition (ESWC) is possible but it may still require workers to interact with energized equipment. The possibility of an arc flash occurring in an ESWC is one of the most severe problems in the electrical industry.
An arc flash, also called a flashover, is a sudden electrical explosion or discharge that happens when electric current travels through the air from one conductor to another. According to Electrical Safety U.K., an arc flash can reach 20,000°C, which is four times the heat of the sun. The resulting sound is similar to a firecracker popping or a gunshot. Examples of arc flash occurrences include lightning and the use of an electrical arc welding machine.
This phenomenon may happen at a small scale such as whenever equipment is being installed or removed, or when disconnecting switches. It can be damaging in a split second, producing fires or major injury to workers who come into close contact with it. When an arc flash occurs, the results can be extremely violent, and if a person is in close proximity to the flash, they can suffer injury or even death.
An arc flash can be caused by an electrical fault in a power distribution system. Faulty wiring, loose connections, failure in the electrical system of a building or structure, or even faulty equipment can also cause an arc flash. It may occur in small spaces, such as a crawl space under a house. It can also occur in large spaces, such as a basement, or in a machine room.
Workplace Safety Awareness Council has given examples of its causes in their handouts on arc flashes. They are the following:
Typical injuries and results from an arc flash include:
It is also possible that an explosive force (known as an arc blast) will be formed, depending on the severity of the arc flash.
Although the possibility of an electric arc forming is low, the severity of the resulting damage can be severe. Control measures can be implemented to minimize the risk of an arc flash occurring in the workplace. The National Fire Protection Association (NFPA) details how to comply with the Occupational Safety and Health Administration (OSHA) regulation through the NFPA 70E standard.
NFPA 70E: Standard for Electrical Safety in the Workplace® (2015 edition) addresses electrical safety and contains the requirements to perform shock and arc flash hazard management.
NFPA 70E is a national consensus safety standard that identifies safe work practices to ensure workers’ safety from electrical hazards. According to NFPA 70E, only trained and qualified employees are permitted to work on or near exposed energized electrical parts, and they must supervise unqualified personnel who are in the proximity of the hazard. NFPA 70E states “This standard addresses safety of workers whose job responsibilities entail interaction with electrical equipment and systems with potential exposure to energized electrical equipment and circuit parts.”
Eliminate manual tasks and streamline your operations.
NFPA 70E has developed specific approach boundaries designed to protect employees while working on or near energized equipment. In the Informative Annex C of NFPA 70E (2015 edition), an illustration was given on the limits of approach, which are boundaries for protection in working. Below is an infographic showing the limits of approach:
Limits of Approach
The limit of approach varies among equipment. Some equipment will have a bigger flash protection boundary while others will have a shorter flash protection barrier.
Another effective way to help prevent arc flashes is to use the 4P Model for arc flash hazard management: Predict, Prevent, Protect, Publish.
The 4P’s Approach
In compliance with NFPA 70E, energized equipment should be installed with warning labels, such as arc flash stickers (also known as electrical hazard labels). These warning labels inform workers about the potential of electrical explosion or high voltages.
The 2017 edition of NFPA 70®: National Electrical Code states in Article 110.16: “Electrical system, such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers that is in other than dwelling, and is likely to require examination, adjustment, servicing, or maintenance while energized, shall be field or factory marked to warn qualified persons of potential electric arc flash hazards…The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.”
It also states that labels shall contain the following:
Modifications are made to the labeling in the NFPA 70E. In order to properly protect workers from arc flashes, you will need to provide the following information:
Arc Flash Warning Labels
In the revised version of NFPA 70E published in 2018, one of the major changes was including the hierarchy of controls in its standard regulations. Specifically, the standard now states that the elimination of the hazard must be the first and foremost priority. Performing energized work with PPE as a last line of defense is also heavily emphasized in the latest update on NFPA 70E.
NFPA 70E (2015) classified personal protective equipment into four categories, with each category containing the minimum Arc Rating value for the PPE that is required.
Category 1: Minimum Arc Rating of 4 cal/cm2
Category 2: Minimum Arc Rating of 8 cal/cm2
Arc flashes and electric shocks can result in fatal injuries. Ensuring that you have the right controls in place to minimize the possibility of an arc flash is essential for the safety of your workers and the proper operation of your company. To avoid these dangers, careful management, attention to detail, and technical expertise are required—all of which can be streamlined using SafetyCulture.
Check out other helpful checklists for electrical safety:
Loida Bauto is a content contributor for SafetyCulture. An Interior Designer by training, she began to pursue her passion for writing in 2017. Her interests involve a diverse range of topics such as Disability, Universal Design, and Sustainability, among other matters that aim to improve the world we live in. She is a self-published book author in 2018 and 2021.
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