According to data compiled by the Centers for Disease Control and Prevention, 5 to 10 arc flash explosions occur in electric equipment across the United States each day. Facilities with dense power structures and high levels of potential energy tend to have prime conditions for arc flash events, including substations, data centers, and similar environments. An arc flash releases a significant amount of electrical energy and occurs because of equipment failure contamination, dust, dropped tools and corrosion equipment failure, inadvertent contact with energized parts, dropped tools and several other causes.
During an arc flash, the air becomes ionized and arc flash temperature can get as hot as 35,000 degrees Fahrenheit — three times the temperature on the surface of the sun. The sound from an arc flash can produce noise as loud as a gunshot and hurl molten metal shrapnel.
Arcing faults generate a level of heat and pressure that destroys expensive equipment, causes extensive downtime, and requires costly replacement and repair. The force of the pressure wave can knock workers off their feet or ladders, and even toss people and equipment across the room. The arc flash manifests as an electrical explosion, lasting less than a second. The event produces heat and a pressure wave that can cause significant harm to workers. Injuries include life-threatening burns and, unfortunately, fatalities.
Anyone who works in an environment that has the potential to produce an arc flash needs to wear the proper personal protective equipment (PPE) to ensure their eyes remain safe during their work. The Occupational Safety & Health Administration (OSHA) mandates all employers adhere to certain practices to protect workers from harm because of an arc flash incident, including providing eye protection to anyone who might deal with hazards while doing their job.
Arc Flash Hazards and Safety Standards
Since the 1990s and early 2000s, regulations regarding arc flash and related electrical hazards have been becoming increasingly stringent. Over the past ten years, electricians, electrical engineers and safety personnel have grown in their knowledge and understanding of arc flashes. This increased awareness of the dangers of arc flashes has given attention to the need for system analysis as well as the use of appropriate PPE.
The most effective arc flash safety programs incorporate safety into the workplace by design and include:
- Worker training
- Warning signs
- Personal protection equipment that includes arc flash safety glasses and other arc flash safety equipment.
The industry bible for arc flash safety in the United States is National Fire Protection Association 70E-2012, the Standard for Electrical Safety in the Workplace. This guide contains significant information on the best workplace safety practices, analysis procedures, documentation requirements, and equipment labeling.
It also addresses personal protection equipment selection principles to protect workers against arc flash hazards.
Arc Flash Hazard Analysis
For more than 40 years, OSHA has required employers to assess the workplace to ascertain the presence, or the likelihood, of hazards in the environment. On June 1974, the agency issued 1910.132, General Requirements, under Subpart I, Personal Protective Equipment. Section 1910.132(d)(1) requires, “The employer shall assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE).”
When a job requires exposure of workers to energized equipment that operates at 50V or more, NFPA 70E-2012 says the employer should perform an Electrical Hazard Analysis, to examine arc flash and shock hazards. The purpose of the incident energy analysis is to determine the severity of the of the arc flash hazard at different locations in the system, taking into consideration the available fault current and the arcing fault clearing time.
To calculate these parameters requires the collection of a significant amount of data on the system, including the cable sizes and information regarding the transformer and motor, usually etched on the nameplates, etc. After the employer has conducted the necessary due diligence and data collection activities, it can construct a model of the power system and compute the arc flash level at certain points in the system.
The data also provide the measurements required to calculate changes level on the calculate hazards, such as upgrading protective relay equipment or current-limiting fuses. The measurement for the arc flash incident level is expressed as calories per square centimeter (cal/cm2). The Cal/Cm2 formula calculates the working distance from a piece of equipment and assigns a hazard level based on the distance.
The IEEE Standard 1584-2002, IEEE Guide for Performing Arc Flash Hazard Calculations, provides a practical calculation model employers can use to calculate flash hazard levels on power systems operating from 208V to 15kV. Although not a requirement, NFPA recommends this option for assessment of the potential impact of arc flash mitigation solutions.
Arc Flash Safety Glasses
Most of the eye and face protection in today’s marketplace has been designed, tested, and manufactured in accordance with specifications provided by the ANSI Z87.1-2010 standard. Manufacturers of arc flash safety glasses protection use a variety of materials, which include acetate polycarbonate, propionate, polyethylene terephthalate glycol (PETG), and steel or nylon mesh. For the best impact and heat-resistant material, look for arc flash safety glasses manufactured from polycarbonate material.
Arc flash safety glasses must meet compliance requirement and deliver in terms of performance, durability, and style. Overall, your safety glasses should offer a level of protective eye shielding that protects the side of the eyes as well as the face. Arc-rated safety glasses or shield are required at Level II, an arc rating of 8 cal/cm2or higher. But even before that, workers should be wearing safety glasses.
This is why employers must perform an arc flash analysis of incident energy, because it enables workers to figure out where they need proper arc flash safety equipment, such as helmet, clothing, headgear, face shield, gloves, safety glasses, and/or shoes that can resist flames. The equipment type will be based on the arc energy level to ensure all parts of the body that could be exposed to the arc flash are protected by the right PPE.
Here are some considerations for employers and workers purchasing arc flash safety glasses for electrical work:
- Workers on a new construction site will likely need standard ANSI Z87-approved safety glasses for electrical work. When working on repairs, when the voltage is standard US 110 V or workers are involved with low amounts or low voltage, standard ANSI Z87-approved safety glasses are appropriate for this circumstance as well.
- Some prescription safety glasses frames are advertised for arc flash protection. Usually, these frames do not contain metal or they have a very small amount of metal that is encased in plastic. These frames are nonconductive, but they do not provide protection for the rest of your face from an arc. However, some shaded masks will provide eye protection from blinding flash generated by an arc flash.
- Many electricians who work around live high voltage, such as 220, 440, etc., tend to wear face masks that are a green shade. Those who have prescription safety glass may use a clear polycarbonate face mask instead of a green
- The best protective safety glasses for arc flash have a green polycarbonate arc flash protective face mask combined with a clear pair of ANSI Z87-approved impact safety glasses. It enables the worker to keep the safety glasses on at all times to protect the eyes from harm in new construction and low- or no-voltage circumstances. Workers can wear the mask on top of the glasses to increase their arc flash protection levels.
For specific requirements for arc flash protection for the eyes and face, refer to the NFPA 70E standard, which covers the requirement based on the ATPV, measured in calories per square centimeter. Simply determine the calorie rating, and then choose your safety glasses and shield.
Selecting Personal Protection Equipment
Working on or near wires or live boxes makes it essential to plan the use of arc flash safety glasses and other personal protective equipment before starting each job. Arc flash protective clothing must be flame retardant and meet other ASTM International standards. The equipment includes:
Hearing loss protection — Ear muffs and ear plugs protect the ears of workers from the high noise emitted by an arc flash explosion, which can lead to some hearing loss permanently, as well as physical or psychological stress.
Hand protection — Wearing gloves can shield workers from harmful substances and chemicals that cause injuries, such as abrasions, severe cuts, chemical or thermal burns, and skin absorption. They can also be hurt by extreme temperatures.
Body protection — Arc flash explosions can be caused by hazardous materials. Electrical safety standards mandate employers provide workers the necessary arc flash protective clothing to protect the body against arc flash hazards.
Respiratory protection — As required, workers should have respirators available to keep their respiratory system from being contaminated by dust, smoke, gases, sprays, and other airborne mists and pollutants. This equipment should cover the nose, mouth, head, or face to lessen the risk of injury.
Note that manufacturers assign flame-retardant clothing an Arc Thermal Protective Value (ATPV). The ATPV value denotes the amount of incident energy that would cause second-degree burns and represents the amount of protection the clothing provides when an electrical arc encounters the material.
Clothing that meets Level I or Level II protection characteristics would suffice for most people working with electricity. The NFPA 70E electrical safety standards lean toward workers who work in category 3 or 4 hazard situations, which include arc flash. The clothing worn by these workers must meet the ATPV rating minimums throughout the entire life of the garment.
Mitigating Incident Levels and PPEs
A critical part of the mitigation strategies any employer has in place is to minimize the level of hazard — the risk of an incident occurring or the potential severity of an incident. Strategies include administrative controls, warnings, and PPEs. Under no circumstance will the practice of these mitigation techniques and solutions guarantee protection against arc flash hazards. However, workers will have more comfort knowing they can work anywhere, anytime, and feel protected.
The ANSI Z10-2012, Occupational Health and Safety Management Systems identify the following elements of mitigation controls:
- Personal protective equipment
- Administrative controls — work policies and procedures
- Warnings including arc flash safety training
- Engineering controls
- Substitution-less hazard materials, processes, etc., when possible
Again, implementing the above techniques in accordance with the regulatory requirement is not a guarantee. In the case of case of PPEs, injuries sustained during an arc flash event would be “reduced” and “survivable” because of the mitigating effects of items such as arc flash safety glasses and other safety equipment.
Arc Flash Safety Plan
Generally, employers have an ongoing desire to look for the latest strategies to avoid an arc flash explosion and to safeguard workers who may be near an arc flash. The primary purpose of NFPA 70E is to decrease the accidents that happen in the workplace around electrical energy.
This standard includes guidelines for the selection of arc safety glasses selection and other PPEs that could offer great protection in the event of an arc flash explosion. Employers should have an electrical safety program, which includes the following four components:
- A knowledgeable and experienced workforce, qualified to perform the task
- Arc flash safety training, safe work practices and other procedures in place to reduce the probability or severity of an injury
- Controls and hardware in place to reduce the extent/level of the hazard
- Personal protective equipment, including clothing and gloves, and other arc flash safety equipment, to protect the worker in the event of an arc occurrence
The absence of any of the above elements could lead to severe injury and death from arc flash incident. To learn more about arc flash safety training, contact Technical Skills Development Services about our on-site OSHA training program.