Similar but different - How to tell the difference Between Arc Rated (AR), Flash Fire Rated (FFR) and Flame Resistant (FR).
In 2012, NFPA 70E changed the terminology referencing personal protective equipment (PPE); what was formerly referred to as FR (flame resistant) clothing is to be called Arc Rated or AR, according to the standard change. The difference between the two and the reason for the change lies in the fact that ALL clothing with an arc rating (AR) is flame resistant (FR), but not all FR clothing has an arc rating. FR doesn't have any standards applying to any particular hazard. FR traditionally was believed to be generically protective from flame at some level, but this is actually untrue of some fabrics. AR indicates a garment has an arc rating and the level of protection has been determined through testing.