How Dangerous is an Arc Flash Hazard?

February 4, 2011 by Austin Cushing.

(Anchortex-AWS-2011-0001)

As you may be aware, employees working on or in close proximity to high-voltage electrical equipment are required to wear protective clothing, rated by hazard risk category. This personal protective equipment is required for compliance with OSHA and NFPA 70E standards, and can be cumbersome to wear. But is it really necessary?

In a word, yes. Anyone who has witnessed a lightning strike has ample evidence of the awesome and terrible power of an electrical arc, and even low levels of electrical current are enough to injure or kill an unprotected individual. Electrocutions in the workplace cause over four hundred deaths per year, and arc flash blasts can rival conventional explosives in their devastating effects on an area. An arc flash creates intense radiant heat and light in addition to explosive force, which can burn or blind unprotected individuals even if they are not directly struck by the electrical arc.

The best way to prevent arc flash hazards, of course, is to de-energize electrical equipment before servicing it in any fashion. However, the act of de-energizing equipment (throwing the switch on a circuit breaker, for example) is itself an arc flash hazard and lock-out/tag-out procedures to deactivate industrial equipment should not be performed without personal protective apparel specifically rated for the task.

Most people know that when handling electrical equipment, they should wear rubber gloves. More specifically, however, rubber gloves should be voltage-rated and tested for the maximum line-to-line voltage on which they will be working; furthermore, leather protective exterior gloves must be worn over them if they are to be used under conditions in which they could be damaged (by being scratched up, for example.) Furthermore, the NFPA 70E Standard for Electrical Safety Requirements for Employee
Workplaces requires semi-annual glove testing to ensure that gloves continue to perform as expected.

All arc flash PPE requirements also include safety glasses to protect the eyes, a hard hat to provide protection against head injuries, leather safety shoes to reduce grounding, and natural-fiber long-sleeved shirts and pants to provide a basic level of flame resistance. This is the base level of protection considered for ‘everyday work clothing’ upon which additional protective clothing is added to provide a protective solution. NFPA 70E rates various tasks in terms of HRC (hazard risk category) levels from 0 to 4, where 0 is ‘no added protection’ - the aforementioned minimum requirements - and 4 is required for circumstances involving working on energized high-voltage equipment, for example.

For worker safety, employers are required to fully evaluate and document electrical hazards, train employees in understanding these hazards, establish a flash protection boundary, restrict access to systems within this boundary to trained employees with proper protective gear and written authorization, institute lockout/tagout procedures on energized equipment before servicing it (with certain exceptions for life-critical equipment), and audit safety procedures annually. In short, this means ‘do not flip the switch on the 480 volt circuit breaker at your workplace unless you are specifically trained in the hazards, have proper protective apparel, and have written authorization to do so.’ The cost of doing otherwise could very well be your life.

For full compliance with OSHA and NFPA 70E requirements, visit our arc flash protective gear section on americanworksafety.com for arc-rated protective apparel and equipment, or contact our sales department to request quotes on personal protective equipment for your facility, department, or organization. The life you save may be your own.

Posted in Arc Flash, Industrial, American Work Safety, Articles | 1 Comment »