Arc Flash Hazard Analysis

Why Do I Need To Be Concerned With Arc Flash Hazards?
An arc flash is a sudden, massive release of energy from a piece of electrical equipment caused by a fault in the system. The fault can be caused by anything from failing insulation to moisture in equipment to a worker accidentally dropping a screwdriver while working. As electrical systems become more complex and reliability becomes more of a need than a want, more and more workers are asked to work on equipment while it is energized. An arc flash that occurs while a worker is in the proximity can potentially cause severe injury or even death. If an owner is asking an electrician or maintenance personnel to work on energized equipment, the liability of providing a safe environment for the worker to do so falls on the owner.

Where Are Arc Flash Hazard Requirements Found?
Arc flash hazard requirements are found scattered throughout various codes and standards, though most prominently in NFPA 70E – the Standard for Electrical Safety in the Workplace and the National Electrical Code. It is important to note that while the NEC is code and is legally enforceable where it has been adopted, the NFPA 70E is not. This does not, however, mean that the requirements found in NFPA 70E can be ignored – quite the opposite. The Occupational Safety and Health Act is federal law and OSHA has the ability to levy severe fines and penalties to employers who violate it. In arc flash incidents, OSHA leans on their general duty clause which reads as follows:

“Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to employees.”

Because the NEC and NFPA 70E are industry standards and both openly acknowledge the danger of arc flash incidents to workers, OSHA has authority to rigidly enforce either document.

What Is Required To Meet These Requirements?
NFPA 70E requires that employers perform an arc flash hazard analysis on electrical equipment, “conducted for the purpose of injury prevention and determination of safe work practices.” The standard notes that the hazard analysis should identify the Arc Flash Protection Boundary (the distance inside which a person is likely to suffer at least a second degree burn due to the energy released in during an arc flash event) and the appropriate levels of Personal Protective Equipment required.

There are two allowable methods – one is a full Arc Flash Hazard Calculation Study (AFHCS) and the second is via hazard/risk tables found in the standard. It is important to note that a full AFHCS typically requires extensive, sometimes invasive, field survey work to create an accurate model of all components of a facility’s electrical system. This method can be very time consuming, but yields accurate and exact incident energy data and required PPE selection for each piece of electrical equipment. The hazard/risk tables are currently acceptable for determining PPE but provide “typical” results and may leave workers over or under-protected.

Both the NEC and NFPA 70E require employers to provide labels on electrical equipment identifying potential arc flash hazards. NEC doesn’t expound on the content of the label, but NFPA 70E notes that the equipment should be marked with either the required PPE or incident energy (from which required PPE can be determined).

How Often Does My System Need To Be Evaluated?
Per NFPA 70E, a revised system evaluation should be performed every five years, or with major changes to the electrical system. Major changes not only include changes or additions to the distribution system within a facility, but also changes to the utility distribution network. Note that utility companies are NOT required to notify facilities of changes to their network which may impact available short circuit ratings or arc flash calculations. The onus is on the end-user to make sure their information is up to date.

Where Do I Go From Here?
If your facility already has had an arc flash evaluation performed, is it up to date? Have there been any changes to your system (known or unknown) since the last time the study was reviewed?

If you have not yet had your system analyzed and are concerned about worker safety and potential liability exposure, do you know where to start?

Barton Associates has extensive arc flash experience, ranging from new facilities to aged, existing systems, from small stand-alone buildings to large campuses. If you would like more information on how to make sure your existing information is up to date or discuss options for a new analysis, please contact Wes Stiles, PE at 717-845-7654 or

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