The electrical industry has much to gain from incorporating arc-rated (AR), flame resistant (FR) garments to help mitigate the impacts of arc flash hazards. AR/FR daily wear balances the comfort and mobility of workers with proven and consistent protection that can save lives. Especially when compared to the task-based donning of AR/FR garments for specific hazardous tasks, which is fraught with human error, AR/FR daily wear, a consistent last line of defense, can help parties address the emphasis on human error in the risk assessment as directed by NFPA 70E without compromising performance.
As part of an AR/FR daily wear system, layers play a helpful role in building a want-to-wear experience for AR/FR personal protective equipment (PPE). From incorporating performance base layers, which help wick moisture away from the skin and regulate body temperature, to arc-rated coats and jackets, layers align the AR/FR garment system with the worker’s environment. Layers are even beneficial in meeting NFPA 70E PPE Categories and/or exceeding incident energies; however, accounting for the arc rating of a complete AR/FR PPE system requires special attention.
It might stand to reason that the various layers can be “added together” to achieve the total arc rating of the system. In practice, though, determining the total arc rating must be done in one of the following ways:
- If a single layer of the AR/FR garment system meets the necessary incident energy or category arc rating criteria of the specific job task, then the total garment system is qualified for that job task. Keep in mind that the outermost layer must be arc-rated, even if it is not the highest rating of the system.
- If a combination of AR/FR layers works together to achieve a higher level of arc flash protection than each layer alone is rated for, then the complete layered clothing system must be tested for arc rating using the ASTM F-1959 protocol in a qualified lab.
Safety managers cannot arrive at the combined arc rating of a system by adding together each layer’s arc rating—so, for example, an 8 cal/cm2 shirt and 12 cal/cm2 jacket may not achieve a 20 cal/cm2 total system arc rating. The ASTM F-1959 protocol mentioned above clarifies either the arc thermal performance value (ATPV) or the Energy Breakopen Threshold (EBT) to designate the system’s formal arc rating. If the ASTM F-1959 test is not performed on the system, then the highest arc rating of the various AR/FR garment layers determines the total system’s arc rating.
Because the ASTM F-1959 test must be conducted in a certified lab, many end users are unable to determine the total system’s arc rating without assistance. One of the many advantages of working with a reputable AR/FR fabric manufacturer—like Westex by Milliken—is their ability to provide layered system test results to confirm the combined arc rating of AR/FR pieces. ASTM F-1959 is a standardized fabric test method, so many fabric and garment manufacturers have a wealth of data to draw from when specifying garments. Even if the layered system in consideration has not yet received a clothing system arc rating, garment or fabric manufacturers may perform the testing requested.
Not all fabrics are created equal, and never is this more apparent than when considering AR/FR fabrics for layered AR/FR garment systems. Westex by Milliken, a Milliken & Company business, offers a comprehensive range of blend, cotton, cotton-rich and aramid fabrics proven for real-world performance. A layered AR/FR garment system can be elevated by incorporating the new Westex® DH base layer fabric, which offers performance benefits akin to streetwear base layers without sacrificing the trusted protection. No matter the need, Westex by Milliken has you covered.
About the Author
Scott Francis is the Technical Manager for Westex by Milliken. Involved in the safety industry since 1991, Scott has extensive experience with protective apparel fabrics and apparel programs. He participates in a number of industry organizations and frequently addresses trade associations regarding relevant safety topics.