Arc flash protection

The NFPA 70E-2004 standard clearly states ways to protect workers from arc flash dangers.

These are more than electrifying statistics:

• One person is fatally electrocuted in the workplace every day.

• Electrocutions are the fourth leading cause of traumatic occupational fatalities. 

• More than 2,000 workers are sent to burn centers each year with electrical burns.

• An average of 4,000 non-disabling and 3,600 disabling electrical contact injuries in the workplace occur annually in the United States.

Backed by these statistics, the recently published NFPA developed the 70E-2004 standard. It is the new “how you work on it” standard in electrical safety that is in concert with the “how you build it” approach of the National Electric Code’s (NEC) NFPA 70 construction standard. It gives the industry a more complete picture of how to protect employees from electrical shock and arc hazards.

Worker protection from arc flash dangers is not new. In 1994, OSHA instituted an apparel standard, CFR 1910-269, to help protect workers with arc- and flame-resistant clothing. Simply, it stated that clothing could not increase the extent of injuries resulting from electrical accidents. It spurred the development of arc-resistant materials and protective clothing lines for workers.

NFPA 70E is the first standard to specifically require arc flash personal protective equipment (PPE) while working on or near live power greater than 110 volts. The NFPA 70E-2004 standard resolves many of the issues raised by the 2000 version.

No tolerance policy
The new standard follows the 70E-2000 version’s no tolerance policy on electric shock/contact and predicted second-degree burn in arc flash exposures. The NFPA 70E-2004 standard features the following components to accomplish this goal:

• A strong preference for de-energizing equipment whenever feasible.

• Training all workers exposed to potential arc flash or electrical shock hazards. This includes operators who may be task-qualified to operate a power disconnect; electrically unqualified workers; and office personnel. All must be trained in the basics of electrical safety to prevent unqualified persons from entering live work and arc flash zones.

• Creation of arc flash boundaries to complement the shock hazard approach boundaries.

• Require management to initiate an energized work permit process for all energized maintenance and repair work except for testing, troubleshooting and other specific instances. This makes live work the exception rather than the rule.

• The committee believes these are the most protective PPE requirements in the world. It also believes that if the rules are heeded, the severity of electrical accidents can be reduced and could even eliminate most electrical fatalities in the workplace.

PPE specifics
The standard now identifies, in simple terms, what should be worn in most work situations with electrical hazards. The standard correlates levels of protection with specific clothing recommendations, yet avoids design restrictions to allow innovations in protection, donning, doffing, fit and worker comfort.

The hazard/risk category is defined by two methods: a table method (see table on page 36) that gives a category for each work task, and a calculation method that allows direct prediction of energy levels the worker is exposed to in a given situation. The calculation method is more involved but allows for reduction or elimination of some PPE by engineering out the hazard.

Predicted exposures of greater than 40 cal/cm2 are not addressed by the standard. The 70E rule-making committee members were uncomfortable advising what PPE should be used at this exposure level. Working on energized equipment and circuits with high short circuit current and greater than 40 cal/cm2 exposure could be compared with smoking in a dynamite shed, and the committee recommends engineering guidance for PPE selection for exposures over 40 cal/cm2.

Other important NFPA 70E-2004 changes
There are a few other important changes in the NFPA 70E-2004 when compared with the 2000 version:

• An arc-rated 8 cal/cm2 face shield is now required for all Hazard/Risk Category 2 tasks.

• Hazard/Risk Category 1 is reduced from 5 cal/cm2 to 4 cal/cm2.

• Working in the Prohibited Approach Boundary is considered as dangerous as touching the energized part.

• The qualified person is now required to receive safety training on the hazards involved.

• The multi-employer relationship requires the owner and contractor to inform each other of existing hazards, PPE required, safe work procedures, and emergency procedures applicable to the work involved.

• For Hazard/Risk Category 2 tasks not requiring shock protection, the standard recommends a heavy-duty leather (>12 oz./sq. yd.) glove be worn. A good-quality, all-leather work glove meets this requirement.

Click here to view the arc flash personal protection requirements.

Hugh Hoagland is an electrical safety consultant who can be reached at hugh@ArcWear.com.

Published in the September 2005 issue of Contractor Tools and Supplies magazine.

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