Understanding Arc Flash Terminology

As a part of our summer safety series, this blog covers arc flash terminology. Today's blog is provided by our partners at National Safety Apparel (NSA) 


The electrical safety industry and standards have evolved over the last few years. With this, the terminology has changed, too. Whether you're new to arc flash or you've dealt with arc flash PPE in the past, it is important to note these changes and ask questions about anything you're unsure of. Below are a few commonly asked questions relating to the new arc flash terminology.

NSA Arc Flash Kit


Is HRC the same as CAT?

 In short � yes.


HRC: Is an acronym for "Hazard Risk Category"�. Before its elimination in the 2015 update to NFPA 70E, HRC was used when discussing the minimum level of protection in flame resistant and arc flash clothing needed for a certain task.


CAT: Is short for PPE "Category"�. The most common categories are CAT 2 and CAT 4, but CAT 1 and CAT 3 also exist. The arc rating of a garment determines which CAT it belongs to.  Many FR and arc flash PPE companies have transitioned to using CAT to replace HRC. PPE Category levels are commonly used by those following NFPA 70E as a guide for the minimum level of protection needed for a certain task.


Is my FR clothing AR?

 In short � maybe. All AR (arc-rated) garments are flame-resistant (FR) but not all FR garments are arc-rated. If FR clothing is not given a specific arc rating and CAT, it is not AR. It is important to know the difference between the two acronyms, FR & AR: 


FR: Short for "Flame-Resistant"�. Clothing and garments made from FR materials have the ability to self-extinguish (with an after-flame of 2 seconds or less) and will not melt or drip. This is tested per ASTM D6413, commonly referred to as "the vertical flame test"�.


AR: Short for "Arc-Rated"�. AR is used to describe personal protective equipment (PPE) and fabrics designed to offer protection against an electrical arc flash. Arc-rated fabrics are tested to ASTM D6413 to determine flame-resistance, as well as a variety of other test methods. All of the required testing can be found in ASTM F1506, which is the performance standard for materials used to make arc-rated clothing for electrical workers. One of the required tests is ASTM F1959, which is used to determine a fabric's arc-rating, which is the level of incident energy that it will protect against.


What is the difference between ATPV and EBT in arc flash PPE?

ATPV: Stands for Arc Thermal Performance Value, a type of arc rating. It measures the incident energy that results in 50% probability of a 2nd degree burn. When someone refers to an arc rating for their arc flash PPE, they are often referring to the ATPV that a garment has achieved. The ATPV arc rating is typically displayed as "__ cal/cm2"� or just "__ cal"�. The "__"� being replaced with whatever the test result value is � ex. "12 cal/cm2"� or "12 cal"�.   


EBT: Stands for Energy Break-open Threshold. A type of arc rating that measures the amount of incident energy resulting in 50% probability that the material will break open. Materials with an Ebt arc rating tend to offer more thermal protection but are not as strong as fabrics with an ATPV. Arc ratings that are Ebt are labeled as such.


Typically, both EBT and ATPV are considered equally protective. It is possible for a fabric to have both an ATPV and Ebt rating but the lower of the two must be reported on the garment labeling.


Which arc flash CAT or ATPV is right for your job?

A hazard assessment must be done to determine that answer. Once you receive your results, it is vitally important that you fit your entire team with the proper PPE to achieve compliance to industry standards. Having a greater understanding of the aforementioned terminology will help make the process of selecting FR/AR clothing easier and ensure compliance.


Looking for more ideas on how to provide your employees with the PPE they need to protect themselves from heat stress and arc flash risks? Talk to one of our safety advisors today.

Arbill is a safety solutions company. We are all about protecting your workers in the workplace. Our mission is to keep workers safe and return them home safely at the end of the day. Visit arbill.com for more information about being safe and subscribe to Safer Every Day, the definitive digital magazine for workplace safety.