Electric arc flashes are often too quick to be seen, but they can cause serious damage. Here’s what you should know to protect your workers.
According to the Occupational Safety and Health Administration (OSHA), electric arcing, commonly referred to as arc flash, occurs when current passes through air between two or more conductors or from conductors to the ground. Many events can initiate an electric arc, such as a tool falling onto an energized conductor, a worker touching an energized conductor thought to be de-energized, voltage testing with inappropriate instruments or operation of a switch that is internally damaged. Loose connections and environmental factors, such as water intrusion and conductive dusts, can also initiate arc flash events.
Arc flash temperatures can reach 35,000 degrees Fahrenheit and can affect workers within several feet of the event. Arc flashes can also consist of multiple energy events in rapid time that combine intense blast, mechanical and acoustic energy along with the release of intense thermal energy.
The arc flash hazard has been inherent in industrial and commercial facilities since the beginning of electrification in the late 19th century. What is relatively new is the evolution in science and technology necessary to understand, quantify and manage arc flash events. Much has been learned since the early 1980s to influence changes in electrical safety regulations, codes and standards. Historically, electric shock was used to describe injuries from mishaps involving contact with electricity during which electric current passes through the body.
A person doesn’t need to make physical contact with an energized conductor or be part of the electrical circuit to receive severe arc flash burns. The victim may be several feet away from energized conductors or equipment and be severely injured by the intense thermal energy transfer of an arc flash. The most recent analysis of electric shock and arc flash injuries and fatalities is available as a free download from the Fire Protection Research Foundation.
To raise awareness in risks and prevention of arc flash injuries, the National Institute of Occupational Safety and Health (NIOSH) produced a 25-minute educational video introducing viewers to arc flash hazards and discussing leading causes of arc flash incidents. The video includes personal testimony from arc flash victims and highlights the importance of the requirements and guidance in NFPA 70E “Standard for Electrical Safety in the Workplace.” The video is available in DVD and live streaming formats on the NIOSH website, and Electrical Safety Foundation International (ESFI) has partnered with NIOSH in making this video available in both English and Spanish.
Identifying Worker Safety Needs
OSHA regulation 1910.132(d)(1) General Requirements – Personal Protective Equipment requires that you, as an employer, “assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE).” Comprehensive solutions to electric arc hazards involve application of the hierarchy of safety controls as described in occupational safety management systems standards, such as OHSAS 18001. The hierarchy includes consideration of choices in electrical system design that can help reduce the likelihood and/or severity of arc flash events through elimination, substitution and engineering controls. Where electric arc hazards haven’t or can’t be adequately controlled by design solutions, NFPA 70E addresses in detail the remaining controls in the hierarchy: warning (including arc flash labels), administrative controls (including de-energization and other safe work practices) and PPE.
The 2015 edition of NFPA 70E provides two methods to help assist employers in assessing risk and determining arc flash PPE needs, per OSHA regulations. One method involves an engineering study to determine incident energy, or thermal energy that would strike a worker a specific distance from the arc. This method provides information that can help employers identify and prioritize opportunities to reduce risks through engineering design solutions, as well as determine PPE requirements. A second method for helping employers select PPE involves the use of several tables that describe common work tasks and recommended PPE. This method can offer certain levels of protection for situations where an engineering study has not been completed. Both methods are dependent on maintenance of fuses, circuit breakers and other protective devices to provide reliable detection and clearing of high currents characteristic of electric arc hazards. If the overcurrent protective devices do not function as designed, the selected PPE may not serve as adequate protection to prevent serious and perhaps fatal injury. It is up to the employer to perform a job hazard assessment and determine what PPE is right for their workers.