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An electrical arc flash is a short circuit where electricity unexpectedly uses the air and flashes between conductors, such as from one wire to another. The blast is very powerful. It is a hazard and is the cause of half of all electrical fatalities. In the United States, the federal agency OSHA regulates work place safety for arc flash. - OSHA, the Occupational Health and Safety Administration, issues Code of Federal Regulations 29 CFR. Part 1926 Subpart E and Part 1910 Subpart S set standards for warning, prevention and protection against electrical hazards, and this includes arc flash. OSHA also bases its standards on recommendations set by the National Fire Protection Association.
The National Fire Protection Association publishes NFPA 70E: Standards for Electrical Safety in the Workplace. Employers are expected to follow them, though they are not mandated. OSHA issues citations and fines if an arc flash incident happens because of violations. - Employers are to identify and analyze possible arc flash situations. This information is to be used to help develop preventive measures.
The analysis is to include a flash protection boundary that is to be calculated with the use of a mathematical formula. The formula includes parameters such as the capacity rating of a transformer, the time of the arc flash, the distance from an arc source to the worker for second-degree burns to occur, and the bolted fault capacity. The bolted fault capacity is the current that occurs in a short circuit where the wires, such as conductors, are joined or "bolted" together. This happens due to errors in installation. - Circuits must, if possible, be de-energized by turning them off, and this may be done by shutting off circuit breakers, for example. Capacitors are common electrical components that manipulate current by storing energy. Special care must be taken to ensure that they are discharged, and this is also part of the de-energizing process. The circuits must be locked and tagged, and their shutoff state must be verified with the use of test equipment. The circuits, equipment and tools must be properly insulated and grounded. The tools used should be rated for use on live circuits.
- Electrical equipment is to be marked or labeled with hazard warnings detailing specifics such as voltage, current and power. Tags or signs must be used to warn employees of the possibility of arc flash and that injury or fatality may be the result. These precautions are expected to provide enough information so that employees can protect themselves against arc flash dangers.
- Other preventive standards must guard against the shock, blast, trauma and burns that may result from an arc flash. Flame resistant clothing must be worn to protect against fire. This includes shirts, pants and coveralls. The eyes, face, head and extremities, such as hands and feet, must be shielded and protected, and respiratory devices must be supplied. Employees must be trained in safety measures.
