When the insulating medium no longer offers sufficient resistance to the flow of electric current, an arc can occur. If enough electrical energy is present, this arc will ionize the air surrounding it causing a traumatic and explosive event called an arc flash.
This event can result in extreme temperatures (currently beyond the testing limits of most lab equipment), which may cause life changing human injury up to and including death and catastrophic equipment damage.
The main risk associated with arc flash is ignition of polyester, cotton, or other non-flame resistant clothing. When this ignition occurs, the worker may receive significant burn injuries resulting in death or months in burn units. Workers may also have vision loss or damage due to the immense light emitted in the visible, UV, and infrared spectrums.
Arc flash events may be the result of human error (i.e., dropping metal tools into the circuit or panel enclosures), equipment failure (i.e., a failed contactor), inadequately rated electrical test instruments (i.e., a ‘Wiggy’ or an inexpensive digital meter with inadequate fusing), poor craftsmanship (i.e., loose wire nuts or incorrect terminations), pest control issues (i.e., spider webs or rodents crossing phase conductors), and an innumerable assortment of other factors.