To aid in the selection and implementation of PPE in areas at risk for arc flash or flash fire, industry standards from the National Fire Protection Agency (NFPA) provide guidelines and reference charts relating environmental risks to the appropriate level of protection required. However, the variety of flame-resistant (FR) fabric choices and garment types available, combined with the diverse range of environmental elements that may be present and differing severities of hazards, can make proper selection a difficult task. Understanding industry standards and the FR fabric options is essential in determining the proper FR apparel for an application environment.
FR apparel is designed for continuous wear in designated areas where intermittent exposure to flame or heat is possible. Ordinary work apparel will ignite and continue to burn if exposed to an ignition source such as flame or electric arc. Conversely, FR garments are intended to resist ignition and prevent the spread of flames, diverting them away from the immediate area of high heat impingement.
FR apparel also is designed to self-extinguish almost immediately upon removal of the ignition source. By reducing the length of time the wearer is exposed to flame, FR garments reduce the extent of the burn injury. FR clothing additionally resists breaking open and does not melt or drip when exposed to flame, maintaining a barrier that insulates the wearer from heat.
Arc flash is an explosive blast of flame, debris, sound and force that occurs due to the passage of substantial electric current through ionized air. While an arc flash event usually lasts under 1 second, it can reach up to 35,000 degrees F and send molten metals at high velocity. Arc flash is the cause of up to 80 percent of all electrical injuries, often due to ignition of clothing and subsequent burns. Each year, more than 2,000 employees are admitted to burn centers with severe burns due to the ignition of clothing that resulted from arc flash incidents.
A flash fire is a sudden, intense fire caused by the ignition of flammable solids, liquids or their vapors, gases or dust. It is characterized by high temperature – creating a heat flux of approximately 84 kW/m2 – and a duration of typically 3 seconds or less, as well as considerable shock waves and a rapidly moving flame front. This flame front can be a combustion explosion, spreading with unusual speed. Witnesses may see the flame race across the surface of a flammable liquid or through a cloud of dust or gas.
While commonly used in areas with the potential of arc flash and flash fire, FR apparel also may be required in welding and other environments prone to sparks and slag, as well as the presence of molten metals or close proximity to open flames.
Under OSHA’s Genderal Duty clause, it is the employer’s responsibility to identify risks and hazards in the workplace, as well as to seek out appropriate protective garments and equipment for the protection of workers. In making this hazard risk assessment, the employer must consider the risks present and also the most appropriate means of addressing those risks. FR protective apparel can be an important part of an action plan to address these concerns in environments with ignition risks.
The potential need for FR apparel also is addressed in 1910.269, the final rule on electrical protective equipment. This applies to electric utilities and co-generation plants where maintenance is performed on existing facilities. It states that the employer “shall ensure that each employee who is exposed to the hazards of flames or electric arc does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of the injury that would be sustained by the employee.”
To meet OSHA’s need to further address electrical hazards in the workplace, the National Fire Protection Association (NFPA) developed the NFPA 70E standard, containing detailed instruction on electrical safety-related work practices and procedures for safeguarding employees during activities such as operation, maintenance and demolition of exposed energized electrical conductors or circuit parts. NFPA 70E states that “employees shall wear flame-resistant clothing wherever there is a possible exposure to an electric arc flash,” and it provides comprehensive, multi-step instructions on how to protect electricians and maintenance employees from electric arc hazard. This includes Table 130.7(C)(9), used to determine the hazard/risk category (HRC) – a term for categories of clothing and PPE recommendations based on the expected arc energy, as well as the risk of arc in the particular job, task or equipment.
Electric arc is measured in calories; one or two calories/cm2 will cause second-degree burns. Clothing/PPE worn in the category may exceed the category requirement, but it may not be less than that required by the category.
The 2009 revision of NFPA 70E addresses the role of host and contract employer responsibilities regarding worksite electrical hazards. The host employer is responsible for advising the contractor of known hazards and other information about the worksite. The contract employer is responsible for instructing his or her employees in the hazards communicated by the host employer and for ensuring that the contract employees follow required rules and work practices, including appropriate work apparel.
The NFPA 2112 standard expands on NFPA 70E by acting as a means of certifying fabrics and findings suitable for use in FR clothing to be worn as protections against possible flash fire exposure. Specifically, the NFPA 2112 Standard on Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire details “the minimum design, performance, certification requirements and test methods for flame-resistant garments for use in areas at risk from flash fires.” The standard also requires certification of garments by a third party, such as Underwriters Laboratories. Its companion standard, NFPA 2113 Standard on Selection, Care, Use and Maintenance of Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire, additionally is used for specifying the FR apparel suitable for a flash fire hazard.
NFPA 2112 serves as the standard for all FR fabrics in the United States and, in addition to the usual fabric performance requirements for flame resistance, heat resistance and thermal shrinkage, this standard addresses testing the flame resistance of each fabric layer as well as thermal protective performance (TPP) testing. FR clothing must demonstrate a predicted body burn of less than 50 percent in a mannequin test in order to comply with NFPA 2112. NFPA 2113 provides guidance in the selection and specification of flame-resistant garments, including workplace hazard assessment. Other sections cover use, care and maintenance recommendations.
A final standard often used in the specification of FR apparel is the ASTM F 1506 Specification for Flame-Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electrical Arc and Related Thermal Hazards. This standard covers performance properties of textile materials to be used for wearing apparel by electrical workers exposed to electric arcs. This includes a general requirement that thread, findings and closures used in garment construction do not contribute to the severity of wearer injuries in the event of exposure to an electric arc.
Employees must wear FR clothing that both conforms to the requirements of ASTM F 1506 and has an appropriate arc rating or arc thermal performance value (ATPV). Breakopen threshold energy (EBT) can be used instead if the ATPV cannot be calculated because of fabric break open – which is the energy level with 50 percent probability of fabric breaking open before second-degree burns occur. Garments conforming to the requirements of ASTM F 1506 must be labeled with a tracking code, a statement that the garments meets the requirements of ASTM F 1506, the manufacturer’s name, size information, care instructions and fiber content and the arc rating (ATPV or EBT).
Inherent vs. treated
Knowing the basic differences between “inherent” and “treated” FR technologies also is important for those responsible for evaluating, selecting and maintaining FR garments. Blended FR fabrics, which contain blends of treated and inherently FR fibers, attempt to balance the strength and weaknesses of each fiber type.
In inherently FR fabrics, flame resistance is an essential characteristic of the fiber from which the textile is made. Because the actual structure of the fiber itself is not flammable, the protection it affords is permanent – it can never be worn away or washed out. When exposed to flame, inherently FR fiber swells and becomes thicker, forming protective barrier between the heat source and the skin. This protective barrier stays supple until it cools, giving the wearer vital extra seconds of protection to escape.
Treated fabrics are treated with a flame-retardant chemical to make them flame-resistant. The fibers used in these fabrics, such as cotton, normally are not considered protective but become flame resistant because of the treatment. Unlike fabrics made with inherently FR fibers, chemically treated FR fabrics may have their flame-resistance properties diminished or removed completely depending on how these fabrics are laundered, as well as which chemicals they are exposed to in the work environment.
It is for this reason that the uniform provider selected for FR apparel should be knowledgeable in the techniques and specifications for proper laundering of these garments. Additionally, fabrics made from treated synthetic fibers, which are extruded with a flame-retardant chemical in the fiber-forming process, become flame-resistant for the life of the garment because the flame retardant cannot be removed by wear or laundering.
FR apparel is critical in applications where risk of exposure to flame or heat is possible. It similarly is critical for those charged with specifying FR apparel to determine the proper protective clothing for the environmental risks present. Compliance with industry regulations and standards, as well as a solid knowledge base of the FR apparel options available, ensures the employer’s responsibility of safeguarding employees from workplace hazards is met.
Randy Kaminsky is director of procurement at AmeriPride Services Inc.