A new phrase, arc rated or "AR," is trending in the industry of personal protective equipment. Unfortunately, it has caused some confusion regarding clothing that is fire-resistant, abbreviated to "FR." The simplest and most basic explanation for the two terms is that while AR clothing qualifies as FR, not all FR attire is considered AR.
Why the Distinction Exists
The primary feature of these clothes is their resistance to ignition. If flammable clothing ignites from arc flashes, sudden fire, molten metal and so forth, the hazard can worsen because it can linger long after the initial flare-up, deeply burning the person's skin, potentially impairing the person's ability to breathe or even directly damage the lungs. Conversely, FR clothing is designed so that the potential burn injuries are limited to areas directly exposed to the hazard. FR clothing also insulates a person from thermal hazards, diminishing or preventing the chance of being seriously burnt through clothing that is directly exposed to such ignition hazards; this is where AR comes into play
Judging Statistics and Ratings
Arc rating is a measure of a garment's insulation against arc flashes. The higher the rating, given as "ATPV" or "EBT," the more resilient it is. The AR classification came into existence to encourage and specify the need to resist arc flashes, rather than being stopping at fire resistance. AR clothing will usually give its qualifications within an internal label, though some also give these details on an external label. The external label of an AR garment will explain its level along the Hazard Risk Categories.
AR is Superior, But Not Exclusively So
Because AR garments are also fire-resistant, they protect against flash fires sufficiently enough to commonly be marketed as flash fire protection. Despite this assurance, arc rating does not necessarily equate to similar levels of protection against flash fires. Any AR garment that has passed an FNPA 2112 flash fire test will feature a number indicative of how much of the covered body will burn after 3 seconds of exposure to flame; the lower this number, the more resiliently the fabric protects against burns.