What are the arc flash hazards?

Short circuits and arc faults are very dangerous and potentially fatal to personnel. Exposure to an arc flash frequently results in a variety of serious injuries such as severe burns, damaged eyesight, ruptured eardrums, collapsed lungs, and in some cases, exposure can be fatal. Electricians have been injured even when 10 or more feet from the arc location. Equipment can be destroyed, causing extensive downtime and requiring expensive replacement and repair. Product of arc fault current and voltage concentrated in one place can be enormous, in some cases resulting in tremendous energy released in several forms.

Arc fault generates large amounts of heat that can badly burn human skin and ignite clothing more than 10 feet away. Temperatures at the arc can reach as high as 20000 degree Celsius or approximate four times the temperature of the Sun's surface. Even curable burns can result in tissue injury that can take months to heal. The high arc temperature vaporizes the conductors in an explosive change in state from solid to vapor.

Tools, meters, nuts, bolts in the path of an arc blast may well become projectiles. The arc blast often causes equipment to explode ejecting parts, insulating materials, and supporting structures with life threatening force. The explosive expansion of the surrounding air can create pressure waves able to blow personnel off their feet. Total force on a person standing in front of an open enclosure can well exceed 1,000 lbs. Such forces crush a person's chest breaking bones, puncturing lungs and other organs. Force like this can even propel workers into walls, windows and other equipment exposing to shock hazard due to touching energized conductors and causing additional trauma. Workers can also be injured by falling from ladders or other unstable and non-secure positions. Even if the blast is not powerful enough to propel the worker, arc fault testings indicate that severe head tossing often occurs. These cause whiplash type injuries with the possibility of brain damage.

Intense ultraviolet (UV) light created by arc flash can damage the retina in the eye, cause blurred vision, burning sensations, severe headaches. If proper eye protection is not worn, ejected materials and flying particles can come in contact with the eye and cause further damage. Hot vapors can injure lungs and impair breathing. Hearing can also be lost or damaged by the loud noises and extreme pressure changes created by arc blasts. Test data has shown arc blasts to exceed 140 dB equal to an airplane taking off. Sudden pressure changes exceeding 720 lbs/ft² for 400 milliseconds can also rupture eardrums. Psychological effects such as depression, job apprehension, family tensions should also be considered.