Arc Flash Hazards and Proper Precautions
An arc flash is a short circuit through the air. In an arc flash incident, an enormous amount of concentrated radiant energy explodes outward from electrical equipment, creating:
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• Pressure waves that can damage hearing, fracture ribs, collapse lungs, and knock a worker off a ladder or blow him or her across a room
• Pressure waves that can send loose material like pieces of damaged equipment, tools, and other objects flying through the air at speeds in excess of 700 miles per hour
• A high-intensity flash that can damage eyesight and leave a person blind
• A super heated ball of gas with temperatures in excess of 5,000 degrees that can ignite clothing and
cause serious burns over much of the body.
Workers have been injured even though they were 10 feet away from the arc center. Furthermore,
electrical arc flash hazards do not occur only in the presence of high voltage sources.
In fact, locations consisting of many low voltage equipment sources account for the most arc flash incidents.
Each year more than 2,000 workers are treated in burn centers with severe arc flash injuries.
Causes:
Arc flash occurs when electrical current flows between two or more separated energized conducting
surfaces. Common causes of arc flash include:
• Insulation failure
• Buildup of dust, impurities, and corrosion on insulating surfaces, which can provide a path for current
• Equipment failure due to use of substandard parts, improper installation, or even normal wear and tear
• Birds, bees, and rodents snapping leads at connections
• Human error, including dropped tools, accidental contact with electrical systems, and improper work
procedures
Applicable Rules:
Because of the serious risks associated with arc flash, safety standards have been established to protect
workers.
• OSHA regulations require the use of safety signs, symbols, or accident prevention tags to warn employees about electrical hazards that may place them in danger.
• A National Fire Protection Association standard (NFPA 70E) recommend that employers perform an arc flash hazard analysis before allowing employees to work on energized equipment. Although OSHA does not enforce this standard, the agency considers it a recognized industry practice, and OSHA field inspectors may use it as a reference.
• The NFPA standard also recommends PPE and clothing to protect workers as well as addresses the issue of safe flash protection boundaries designed to restrict entry into areas where are flash hazards exist.
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