Frequently Asked Questions
Every worker can be safe through proper education.
Specific events that can cause an arc flash hazard include:
- Use of improperly rated electrical test instruments
- Dropping uninsulated tools into an energized electrical enclosure
- Conductive dust or moisture building up inside electrical equipment
- Rodents and other animals inside electrical equipment
- Improper installation of electrical equipment
- Improper electrical preventative maintenance resulting in equipment degration
- Unsafe work conditions
Personal Protective Equipment (PPE) provides protection after an arc flash incident has occurred and should be viewed as the last line of protection. Arc flash rated clothing / PPE is required when the worker may be exposed to this risk when equipment is open for maintenance (energized or when establishing an Electrically Safe Work Condition), or even when a risk assessment has determined that switching or operation of closed equipment poses risk to the worker. The arc rated clothing requirements for various electrical equipment shall be determined by an arc flash risk assessment as stated in the NFPA 70E.
The NFPA 70E states that a qualified person shall be trained and knowledgeable in the construction and operation of equipment or a specific work method. They must be trained to identify and avoid the electrical hazards that might be present with respect to that equipment or work method.
Another key part of being a qualified electrical worker is passing an annual field audit per the NFPA 70E.
The National Fire Protection Association’s Standard for Electrical Safety in the Workplace (NFPA 70E) defines an arc flash as: A source of possible injury or damage to health associated with the release of energy caused by an electric arc.
An arc flash occurs as a result of a fault or short circuit condition that generates light and heat. These events may result from a phase to phase or a phase to ground fault cause by a worker mishap, equipment degradation or failure, rodents and other pests, improperly rated electrical test instruments, or other general electrical failure. In a typical home, the electrical service is 100-200 amps with a single phase. In large industrial or commercial facilities, these services may be 2000-4000 Amps (or larger) and have three phases. These larger electrical systems create conditions that can cause arc flashes and need to be analyzed in an incident energy calculation to determine the arc flash potential (expressed in cal/cm2).
An arc flash can produce blinding flashes of light, deafening concussive blasts, super-heated shrapnel, and flames hot enough to ignite clothing. Arc flashes cause significant burns and other injuries to workers that have resulted in death or serious harm to workers.
OSHA is the governing body that ensures that employers protect workers from known hazards such as arc flash. The following codes and standards offer methods to protect workers from electrical hazards:
NFPA 70E: This standard addresses employee workplace electrical safety requirements such as PPE requirements, criteria for electrical tools and test instruments, barricading requirements, and other electrical safe work practices.
NEC: The National Electric Code’s purpose is the practical safeguarding of personas and property from electrical hazards.
ANSI Z10: To provide organizations effective resources for continual improvement of their occupational health and safety performance.
IEEE 1584: This guide provides mathematical models for determining the arc-flash hazard distance and the incident energy to which workers could be exposed during their work on or near electrical equipment.
Any worker who may be exposed to an electrical hazard where the risk cannot be mitigated shall be trained on electrically safe work practices. Qualified workers shall always be trained. Arc Flash Hazard avoidance training may also need to be performed for unqualified workers if they will be exposed to a hazard. The NFPA 7oE addresses this in Article 110.2(A).
OSHA can issue a citation for not addressing arc flash as this is a known hazard. They can issue (and have issued) citations under the General Duty Clause and can reference the NFPA 70E within this citation. Workers shall be provided with PPE, tools, and test instruments to minimize risk, but first they must be warned of the risk through an arc flash warning label.
An arc flash risk assessment calculates the incident energy generated during an electric arc flash event based on the parameters of the electrical system. This arc flash study ensures compliance with OSHA requirements to protect workers.
Once the calculations have been made, the electrical equipment shall be labeled to warn the workers of the extend of the hazard. These labels detail the PPE requirements, the nominal voltage of the system, approach distances, and incident energy potential.
Arc flash labels are required on electrical equipment that is ‘likely to require examination, adjustment, servicing, or maintenance while energized.’ Keep in mind that even establishing an Electrical Safe Work Condition (deenergizing electrical equipment) requires that the worker assumes that equipment is energized until all precautionary steps have been completed. The 2018 NFPA 70E addresses this in Article 130.5(H).
While electrical accidents are statistically less likely than other known hazards, electrical incidents are typically much more catastrophic to worker health often resulting in life altering injuries or even death. Arc flash events may result in burns requiring months of hospitalization, physical therapy, surgeries, and other extensive medical care. These horrific events cause extensive liability claims and litigation. Herzig Engineering recommends that all facilities in other than residential application have an assessment performed to determine PPE application and safe working distances for workers who may be exposed to electrical hazards.