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August 10, 2015

Arc Flash Safety Tips

Are Flash Hazard Appropriate PPE Required
An arc flash is a flashover of electric current that leaves its intended path and travels through the air from one conductor to another, or to ground. The results are often violent, including serious injury and death. By some estimates, 30,000 arc flash incidents occur annually in the U.S., resulting in as many as 400 fatalities. Here's some information and advice on arc flash safety hazards from OSHA.

Arc flash can be caused by many things including:
  • Dust
  • Dropped tools
  • Accidental contact
  • Condensation
  • Material failure
  • Corrosion
  • Faulty Installation

Three factors determine the severity of an arc flash injury:
  1. Proximity of the worker to the hazard
  2. Temperature
  3. Time for circuit to break 

Typical Results from an Arc Flash:
  • Burns (Non Flame-Resistant clothing can burn onto skin)
  • Fire (could spread rapidly through building)
  • Flying objects (often molten metal)
  • Blast pressure (upwards of 2,000 lbs. / sq.ft)
  • Sound Blast (noise can reach 140 dB – loud as a gun)
  • Heat (upwards of 35,000 degrees F) 

What must an employer do to protect employees from hazards posed by flames and electric arcs? In general, employers must:
  • Assess the workplace to identify employees exposed to hazards from flames or from electric arcs
  • Estimate the incident heat energy of any arc hazard
  • Ensure that employees exposed to hazards from flames or electric arcs do not wear clothing that could melt onto their skin or that could ignite and continue to burn
  • Ensure the outer layer of clothing is flame resistant under certain conditions
  • With certain exceptions, ensure that employees exposed to hazards from electric arcs wear protective clothing and other protective equipment with an arc rating greater than or equal to the estimated heat energy
  • Provide flame-resistant and arc-rated clothing and other arc-flash protective equipment as required by the electric power generation, transmission and distribution standards.

Arc Flash Protection Methods include:
  • De-energize the circuit
  • Insulation
  • Guarding
  • Barricades
  • Ground Fault Circuit Interrupters (GFCI)
  • Grounding (secondary protection) 
  • Flame-resistant (FR) clothing rated for relevant heat exposures. The FR clothing industry has developed a heat energy rating system for FR fabrics. To identify the appropriate FR clothing to use, the heat energy, measured in calories per square centimeter (cal/cm2), to which workers are exposed needs to be calculated.

Arc Flash Warning Labels
  • Each piece of equipment operating at 50 volts or more and not put into a deenergized state must be evaluated for arc flash and shock protection. This evaluation will determine the actual boundaries (i.e. prohibited, limited, restricted, etc.) and will inform the employee of what PPE must be worn.
  • Once the evaluation is complete an Arc Flash Hazard warning label must be affixed to the equipment and readily accessible to employees who may work on the energized equipment

Additional Resources:

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