The Dangers of Arc Flash

What Is Arc Flash?
An arc flash is an explosion caused by an electrical arc. Temperatures can reach 35,000°F in a fraction of a second, vaporizing conductors and causing a blast wave that can carry shrapnel, molten metal, and toxic gases, and that hits with enough force to throw workers several yards from the blast.

With temperature four times the surface temperature of the sun, arc flash accidents pose a severe threat to workers' safety. An article in EC&M magazine states:

Severe arc-flash burns can cause a slow, painful death, but even when they aren't lethal, they can do serious damage. Hot gases can injure lungs and impair breathing. Even curable burns can result in painful skin and tissue injury that can take weeks or months to heal. However, not all arc-flash injuries are physical. Psychological effects like depression, job apprehension, and family tension can also manifest themselves. Therefore, avoiding any burn is important in terms of time, money, and a person's well being.

Workers aren't the only ones who stand to suffer from arc flash. A single arc flash incident can cost a company between 1 and 15 million dollars in direct and indirect costs. Medical costs, equipment damage, lawsuits, and OSHA fines can severely impact even a healthy company's bottom line.

Arc flash incidents are unfortunately common, and account for almost 9% of all workplace fatalities. According to statistics compiled by CapSchell, Inc., a Chicago-based research and consulting firm, arc flash incidents send between 5 and 10 workers to the hospital every day.

Arc Flash Safety Regulations
Federal law requires employers to assess and protect workers against electrical hazards, including arc flash. OSHA recognizes a number of industry standards for arc flash safety, include the NEC, NFPA 70E, and IEEE 1584.

The cornerstone of a program designed to protect against arc flash is a study of facility electrical systems to identify and assess hazards. This engineering analysis allows employers to take appropriate measures to ensure worker safety, including:

A major component of arc flash safety is labeling of any equipment that can be the source of an arc flash. NEC Section 110.16 and NFPA 70E mandate the use of warning labels, and provide rules for placement and content.

NEC Section 110.16 reads: Switchboards, panel boards, industrial control panels and motor control centers that are in other than dwelling occupancies and are likely to require examination, adjustment, servicing or maintenance while energized, shall be field 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.

To be effective, warning labels should specify information such as approach limits, magnitude of the hazard, and appropriate PPE. Proposed changes to NFPA 70E, to be released in the 2009 edition of the code, will require specific information to appear on warning labels.

In order to properly label equipment, an analysis of arc flash hazards must be performed. This task can be dauntingly time-consuming, but commercially-available software can make the job easier, as described on the next page of this tutorial.