Basics of Arc Flash Hazards

What is an arc flash?

An arc flash is an electric current flowing through an arc outside its normal path where air becomes the conductor of high thermal energy. The Standards for Electrical Safety Requirements for Employee Workplaces defines arc flash hazards as “a dangerous condition associated with the release of energy caused by an electrical arc.” During an arc flash, temperatures can reach 35,000 degrees Fahrenheit, which is more than four times hotter than the surface of the sun.

An arc blast can cause the same conditions as an arc flash but is more intense and can also include strong pressure waves that can damage machinery, throw a person, collapse a lung or rupture ear drums. Arc flashes and arc blasts last maybe a second but can cause serious injury and sometimes death.

What causes an arc flash?

Arc flashes are caused by electrical short circuits and occur “when the gap between conductors or conductors and the ground is momentarily bridged.” While there are a variety of possible trigger events, most of the time arc flashes are caused by human intervention. Examples of such intervention include:

  • Accidental contact with energized parts
  • Tracking across insulation surfaces
  • Tools dropped on energized parts
  • Wiring errors
  • Contamination, such as dust on insulating surfaces
  • Improper work procedures

Why should you concerned about arc flash hazards?

Estimates indicate that 10 to 15 serious arc flash incidents, those resulting in burn injuries requiring treatment in a burn center, occur each day in the United States. The tremendous amount of heat generated by an arc flash makes being anywhere near an arc flash hazard dangerous. In fact, liability and government regulations apply not just to those working with energized equipment but also to every worker in the near vicinity of that equipment.  Unfortunately, there is much confusion about regulatory compliance in regards to electrical hazards.

What is not confusing is that the intense heat caused by an arc flash can cause life-threatening burns and the intense light can cause blindness. In addition, exposure to arcing faults can also cause:

  • Clothing to be set on fire
  • Large shock waves that can blow people off their feet
  • Expanding gases that can cause flying debris
  • Pressure waves that can knock a person off balance
  • Sound waves that can cause ear damage
  • Intense thermal radiation Arc Flash Video
  • Damaging noise levels

How do you protect against arc flash?

The only way to protect against an arc flash is to “de-energize the equipment before approaching it for the purposes of opening it or for working on it.” This includes turning of the power supply, making sure the equipment is de-energized and assuring that stored energy (from capacitors or induced voltage) will not become an issue.

Personal protective equipment should be warn in an arc flash hazard area because it can help protect the head and body against the affects of an arc flash and hopefully prevent the severity of burns, but it may not necessarily protect against harmful light, sound, pressure impulses, toxic gas by-products or ejected debris.

The key for creating a safe work area with regard to arc flash hazards is to “Make injury prevention your overall objective,… and you’ll find your organization will be more than just compliant; it will be a safer place to work.”

About Michael Eldridge

Michael Eldridge is the President and Founder of Safety Glasses USA, one of the web's largest providers of safety glasses and goggles. He's a US Marine Veteran who's particularly passionate about protective eyewear and helping people learn about vision safety. In his spare time he enjoys target shooting, fishing, camping with his family and watching Detroit Tigers baseball. You can follow Michael on Twitter @MikeEldridge73, Google or via the Safety Glasses USA Facebook Page.