Definition - What does Arc Flash mean?
An arc flash is an explosive flash of light that jumps between two points on high powered electrical equipment. When an electrical current jumps between two points it is called an arc. Any equipment that poses the risk of an arc flash, needs to be labelled with a warning. An arc flash can have deadly consequences, thus everyone who works with that equipment should also be aware of the danger that it poses.
Safeopedia explains Arc Flash
The most widely used standard for arc flash labeling is NFPA 7OE. These guidelines require that all potential arch flash equipment have a recording of the nominal system voltage, the arc flash boundary, and at least one of the available incident energy and working distance or the NFPA's arc flash PPE category for the equipment, the minimum arc rating of clothing required, or a site specific description of the PPE required.