One of the most dangerous electrical hazards in the workplace is arc flash. Also referred to as a flashover, an arc flash is a type of electrical explosion that has the potential to cause serious damage to workers and property. Arc flashes occur when an uncontrolled electric current flows between conductors through an air gap, causing a release of a huge amount of energy. A lower path of resistance in the electrical system allows electricity to pass outside of the system and the light and heat traveling through the air between the two points is an arc flash.

Any workplace that works with electricity or electrical equipment are at risk for arc flash, no matter how weak electrical currents are or the level of electricity flowing through the system. In high-voltage systems however, the occurrence of an arc flash will be much more destructive. Larger arc flash explosions typically result in a release of intense heat, reaching temperatures hotter than the surface of the sun. The heat alone can immediately ignite wood and melt metal, damaging equipment in the facility. Although arc flashes last a handful of seconds at most, anyone in the immediate area of the explosion is in danger of getting second- and third-degree burns. 

In addition to the damaging heat produced from an arc flash, these explosions are usually extremely bright, and the UV and infrared light can result in temporary eye injuries or even permanent blindness in some cases. Arc flashes may also cause deafening noises and people not wearing hearing protection can experience long-lasting hearing damage. Finally, electrocution is always a hazard when an arc flash occurs. Arc flashes have the potential to travel through a person and depending on the amount of electricity, it can be fatal.

Organizations with electrical equipment and systems must take arc flash safety into serious consideration. It is important hazards must be evaluated and arc flash warning labels should be utilized wherever high electrical currents exist. Having an effective lockout/tagout program to ensure machines are de-energized helps to prevent arc flash but because arc flashes are so unpredictable, workers must also be provided with the correct arc-rated PPE.

Additional Flashover facts:

  • A flashover is the near-simultaneous ignition of most of the directly exposed combustible material in an enclosed area. When certain organic materials are heated, they undergo thermal decomposition and release flammable gases. Source: https://en.wikipedia.org/wiki/Flashover
  • Flashover normally occurs at 500 °C (932 °F) or 590 °C (1,100 °F) for ordinary combustibles, and an incident heat flux at floor level of 20 kilowatts per square metre (2.5 hp/sq ft). Building features like concealed spaces, lower ceiling heights, room partitions, and energy-efficient or hurricane windows are more likely to contribute to flashover conditions. Source: https://mercortecresa.com/en/blog/what-is-a-flashover-and-how-does-it-occurs
  • Flashover is a thermally-driven event that ends the growth phase of a fire and marks the beginning of the fully developed phase. After flashover, the fire becomes ventilation-controlled and any victims in the compartment become body removals. Source: https://www.usfa.fema.gov/blog/cb-050520.html
  • Recognizing flashover conditions can save firefighters’ lives. Some signs of an impending flashover are: ambient temperatures quickly rising, large volumes of heavy dark smoke, rollover (active flame circulation in the thermal layer), and free burning fire in a ventilation-deficient environment. Source: https://www.fireengineering.com/fire-prevention-protection/kiurski-flashover/
  • Firefighters can take defensive steps to prevent or delay flashover, such as: cooling the upper thermal layer with a fog pattern, creating a buffer zone with a straight stream, planning an evacuation route, and communicating with command and other crews. Source: https://www.usfa.fema.gov/blog/cb-050520.html
Arc Flash Labeling Guide
Practical Solution Guide to Arc Flash Hazards Guide
OSHA Safety Signs Guide
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