What is Arc Flash? (and Why You Need to Label)

By Jeff MacKinnon, P.Eng., PE

Arc Flash Hazard is one of the three hazards that are directly associated with electricity, the other two being shock and arc blast.

CSA Z462-15 defines Arc Flash as:

a dangerous conditions associated with the possible release of energy caused by an electric arc.

When there has been a breakdown in equipment insulation, whether from equipment failure or an electrical worker coming into contact when working on energized electrical equipment.

What Arc Flash Looks Like


The video above is an example of an arc flash in a 100A disconnect, it demonstrates the immense energy released and a typical application.

3 Side Benefits of an Arc Flash Study

There are tons of reasons to have a current Arc Flash Study, and an Electrical Safety Program, here are three side benefits that you may not have thought of include:

  1. As-Builts - When was the last time you incorporated all the redlines associated with your power system?
  2. Enclosure Audit - Are you sure all your equipment enclosures have their doors secured? Are there latches missing?
  3. Document Switching Configurations - Knowing the valid switching configurations for the facility is critical for the study, but not every plant has these written down for the operators.


The Canadian Electrical Code (rule 2-306) requires labels on all electrical equipment that may require energize work to have a warning label that an Arc Flash and Shock Hazard is present. However, that alone doesn't provide enough information to ensure that the electrical worker opening that panel can select the appropriate PPE. Below is an oversized example of a typical label we would recommend.

Sample Arc Flash Label.

It includes all the information that is recommended by CSA Z462 and is easily read and can be audited without much effort. The top warning and first header line is all that is required by the Canadian Electrical Code, the remainder of the information provided allows a trained electrical worker to select the appropriate PPE for the task at hand.

Next Steps

Here I outlined a couple of simple reasons why you should have a current Arc Flash Study - or complete Power System Analysis - for your plant.

If you have any questions about what you read here, please don't hesitate to contact me through the contact page here.


Jeff MacKinnon, P.Eng.,PE