It refers to the ability of a material to self-extinguish upon the removal of an ignition source. FR is a short name for Flame Retardant Protective Clothing. Remember Fireproof Clothing is NOT fire proof.
Hazard Risk Category is the level of arc flash protection clothing you must wear to protect against a minimum level of incident energy measured in calories per centimeter squared. Meaning, electrical equipment, depending upon the energy delivering capability, under fault conditions can cause an explosion, or arc fault of a certain level, again measured in calories per centimeter squared. That explosion can deliver a certain amount of heat to a certain distance. Each level, 0-4, is rated at a certain amount of flame resistance, again measured in cal/cm2. Each level is considered a category.
|FR shirt and FR pants or FR coveralls (1 layer)|
|Cotton underwear plus FR shirt and FR pants (1 or 2 layers)|
|Cotton underwear plus FR shirt and FR pants plus FR coveralls, or Cotton underwear plus two FR coveralls (2 or 3 layers)|
|Cotton underwear plus FR shirt and FR pants plus multilayer flash suit (3 or more layers)|
HRC2 Single layer flame resistant clothing