What is Arc Flash?

By R.W. Hurst, Editor

What is arc flash? It’s a sudden and violent release of energy caused by an electrical fault, where electricity jumps through the air between conductors or from a conductor to ground. This event produces intense heat, light, and pressure — sometimes reaching temperatures hotter than the surface of the sun. Arc flash incidents are among the most dangerous electrical hazards, posing serious risks to workers and equipment alike.

NFPA 70E Arc Flash Training

CSA Z462 Arc Flash Training

Request a Free Training Quotation

An arc flash and arc blast represent a dangerous type of electrical explosion caused by an arcing fault—a condition where current travels through the air between conductors, creating a high-energy electrical arc. This rapid discharge of energy results in an arc flash event that releases intense heat, light, and pressure, posing a significant arc flash hazard to anyone nearby. Because of the unpredictability and severity of these events, personal protective equipment (PPE) is essential for worker safety. Understanding the causes and effects of arc flash and arc blast is critical for preventing injuries in environments where high voltage systems make such incidents possible.

To reduce arc flash hazards, facilities must comply with established electrical safety standards such as NFPA 70E, which outlines requirements for risk assessments, labeling, and proper use of PPE.

What Causes an Arc Flash?

An arc flash occurs when insulation or isolation between conductors breaks down, allowing electricity to travel along an unintended path. This can be triggered by dust, dropped tools, condensation, accidental contact, corrosion, or equipment failure. The result is a high-energy discharge that can ignite clothing, melt metal, and blast molten debris across a workspace.

Various factors, including equipment failure, human error, or other electrical malfunctions, can cause electrical explosions. Some common causes of incidents include:

Equipment Failure: Incidents can occur when electrical equipment, such as circuit breakers, switches, or transformers, fail, resulting in a short circuit or overcurrent condition. This can cause a sudden and rapid release of energy in the form of an electrical explosion.
Human Error: Human error can also cause incidents, such as improper use of tools or equipment, improper installation or maintenance of electrical systems, or failure to follow safe work practices.
Dust, Debris, or Corrosion: Accumulations of dust, debris, or corrosion in electrical equipment can create a conductive path for electrical current, leading to an explosion.
High Voltage: High-voltage electrical systems are more prone to incidents than lower-voltage systems, as the energy released in an explosion increases with voltage.
Equipment Modification: Modifications or repairs to electrical equipment that are not performed correctly or do not meet electrical safety standards can increase the risk of incidents.

Why Arc Flash Is So Dangerous

The temperatures in an arc flash can exceed 35,000°F — hot enough to vaporize copper conductors and create a pressure wave capable of collapsing lungs. The flash also produces a blinding light and deafening sound, which can disorient or permanently injure anyone nearby. Unlike electric shock, arc flash doesn’t require direct contact — being near the source is enough.

Industries and Workers at Risk

Arc flash is a risk wherever electrical systems operate at high energy levels. Electricians, maintenance personnel, utility workers, and anyone working near energized electrical equipment are especially vulnerable. In industrial settings, arc flash is one of the leading causes of severe workplace injuries.

How to Reduce the Risk

Preventing arc flash involves a layered approach:
De-energize equipment before working on it
Use arc-rated PPE based on an incident energy analysis
Apply warning labels and hazard signage
Comply with NFPA 70E and CSA Z462 safety standards
Train qualified workers on arc flash awareness and response

Understanding what arc flash is — and how it occurs — is the first step toward protecting lives and assets. Electrical explosions aren’t just theoretical risks; they happen quickly, often without warning, and the results can be devastating. Prevention through training, proper procedures, and protective gear is essential in every high-energy environment.