What is the difference between arc flash and flame resistant clothing?

The world of PPE can be confusing, and it's not always easy to choose the right gear for a particular application. But when it comes to flame and arc flash resistant clothing, you don’t want to be guessing. Understanding the difference is key to ensuring the safety of the workers you're responsible for equipping.

Arc Flash vs. Flame Resistant

While the gear can sometimes seem interchangeable, there’s a key difference to remember: all arc rated (AR) clothing is flame resistant (FR), but not all flame resistant clothing is arc rated.

FR Clothing

To be considered FR, the fabric must protect the wearer from burns by withstanding ignition or quickly self-extinguishing. In essence, it acts as a barrier to protect the wearer from the hazard.

While OSHA doesn’t define “flame resistant,” it does specify that clothing must be non-melting and must not be made of acetate, nylon, polyester, rayon, or polypropylene unless the fabric has been treated to withstand the hazardous conditions.

FR clothing is not tested against exposure to an arc flash.

AR Clothing

AR clothing, on the other hand, undergoes rigorous testing above and beyond that required for FR clothing. It is exposed to a series of arc flashes to determine how much energy the fabric can block out before the wearer would experience second-degree burns 50 percent of the time. The test results are expressed in calories and generally known as the ATPV (Arc Thermal Performance Value). If holes develop in the fabric before the threshold is reached, the rating is called the EBT (Energy Breakopen Threshold) instead.

The new standard, 2018 NFPA 70E, requires workers to use table 130.5(C) and a series of tables in 130.7(C)(15) to determine the arc flash PPE categories, arc flash boundary, and minimum arc flash ratings necessary for their PPE. Unlike previous editions of the safety standard, it assists working in navigating this process by outlining the likelihood of occurrence and the potential injury severity from an arc flash hazard using a simple yes/no format.

Choosing the Right Protective Clothing for the Job

Both FR and AR materials protect the wearer from burns. However, arc flashes pose one of the most serious risks to workers. Temperatures can reach hotter than the surface temperature of the sun in fractions of a second, and workers may be exposed to hot gases, intense waves of pressure, and shrapnel from vaporized and molten metal particles. Injuries range from minor or severe burns and blindness to hearing and memory loss, broken bones, and death.

What determines the extent of the injuries? Your choice of protective clothing.

Any worker with the potential to be exposed to an arc flash should be wearing AR clothing. OSHA requires arc rated PPE for all employees who work on or near exposed live parts greater than 600V (learn more about How to Protect Your Hands from Arc Flashes).

Industries with arc flash exposure risks include (but aren’t limited to):

• Automotive
• Construction
• Mining
• Petroleum
• Utilities

For workers carrying out lighter-duty work that requires protection from sparks or flames, FR gear may be sufficient. Examples include petrochemicals, electronics, military, and even some welding applications

Conclusion

When deciding whether you need AR or FR clothing, it all comes down to understanding the hazards you’re up against.