An arc flash is usually caused by inadvertent contact between an energised conductor such
as a bus bar or wire with another conductor or an earthed surface. When this occurs, the
resulting short circuit current can melt the conductors and produce strong magnetic fields
that blow the conducting objects apart. This fault current ionises the air and creates a
conducting plasma fireball with arc temperatures that can reach upwards of 20,000 degrees
Centigrade. Severe injury and even death can not only occur to persons working on the
electrical equipment but also to people located nearby.
Arc flash injury can include external burns to the skin, internal burns from inhaling hot
gasses and vaporised metal, hearing damage, eye damage such as blindness from the
ultraviolet light of the flash as well as many other devastating injuries. Depending on the
severity of the arc flash, an explosive force known as an arc blast may also occur which can
result in pressures of over 100 kiloPascal (kPa), launching debris as shrapnel at speeds up to
300 metres per second (m/s).