An Arc Flash is a devastating blast where the electrical energy flows through the air instead of the conductor. This causes a rapid release of thermal energy and results in a violent explosion.

Arc flashes often occur due to equipment failures, the dropping of tools into energized equipment, as well as rodents, snakes, and other pests that get inside the electrical equipment. An Arc Flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. This can occur from simply removing an electrical equipment panel cover!

Arc flashes can occur without warning in a fraction of a second and the temperature can reach 5,000° F, which is hot enough to vaporize copper. The explosion creates pressure waves that can damage a person’s hearing, a high-intensity flash that can damage their eyesight and a superheated ball of gas that can severely burn a worker’s body and melt metal.

Every year, more than 2,000 workers are treated in burn centers with severe arc flash injuries. The flash is immediate, but the results can cause severe injuries that last months, years—even a lifetime. In some cases, they may cause death.

Fortunately, arc flash hazards can be reduced by following safety precautions and using the recommended personal protective equipment.

The pressure waves can also propel loose material like molten metal, pieces of damaged equipment, tools and other objects, through the air.

A hazardous arc flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. Potential places where this can happen include:

• Panel boards and switchboards
• Motor control centers
• Metal clad switch gear
• Transformers
• Motor starters and drive cabinets
• Fused disconnects
• Any place that can have equipment failure

Some of the employees at risk from arc flash hazards include mechanics, electricians and HVAC personnel. The most dangerous tasks include:

• Removing or installing circuit breakers or fuses
• Working on control circuits with energized parts exposed
• Racking circuit breakers in and out of switch gear
• Applying safety grounds
• Removing panel covers
• Low voltage testing and diagnostics

An employer is required to:

• Conduct an arc flash hazard analysis of the workplace.
• mplement qualified and general worker safety training based on the arc flash hazard analysis results.
• Establish shock and flash protection boundaries.
• Provide protective clothing (PC) and personal protective equipment (PPE) that meet ANSI standards.
• Put warning labels on equipment (see example at right). A future edition of the arc flash safety code may require more extensive labeling (inset) that includes flash hazard boundary and PPE levels.