Three Benefits of Using AR/FR Base Layers for Arc Flash Protection
Appropriate base layers for electrical workers are a useful element in an AR/FR garment system.
- By Scott Francis
- Sep 01, 2019
Arc-rated (AR), flame-resistant (FR) garments are a vital part of any thermal hazard mitigation personal protective equipment (PPE) program, and within the electrical industry, is a mainstay for safety managers. Yet, the garments must be worn—and worn correctly—to achieve the highest level of protection against arc flashes. Daily wear garments, as opposed to task-based garments, are worn throughout the workday and can help alleviate some of the human error consequence concerns surrounding PPE. Keeping this in mind, it is helpful to utilize all resources when creating a system that best protects your workers and provides the greatest level of compliance and comfort in the process.
Appropriate base layers for electrical workers are a useful element in an AR/FR garment system. As a multi-functional garment, AR/FR base layers have a wide variety of both performance and protection applications, making the base layers a versatile addition to your safety program. In this article, we will analyze three key benefits of arc-rated base layers.
Meet and Exceed Consensus Standards
A typical streetwear base layer is usually constructed from popular man-made fabrics like acetate, nylon, polypropylene or spandex. These fabrics underneath AR/FR fabrics pose a serious concern for those seeking arc flash protection. When exposed to the extreme temperatures of an arc flash, these types of fibers will melt and can severely damage the wearer’s skin. A key function of AR/FR fabrics is that they will not only self-extinguish when a thermal source, like a flame, is removed; they will also provide some insulation from the heat source to help reduce second- and third-degree body burns. These melting fibers jeopardize heat source insulation by transferring heat to the skin. The molten polymers stick to the skin, causing additional skin damage and longer recovery times.
To comply with the NFPA 70E consensus standard, base layers worn with AR/FR garments may be made of natural fibers so long as they are used within a comprehensive system. These flammable but non-melting textiles must be covered by appropriate AR/ FR garments completely to prevent ignition. By considering an AR/FR base layer, you can meet the NFPA 70E requirement and provide an added layer of flame resistant, arc rated protection.
Assist in Achieving Required Arc Ratings
AR/FR base layers can contribute to the arc rating of a complete AR/FR PPE system. Determining the total arc rating number for a clothing system can be accomplished in one of two ways:
- One AR/FR layer in a clothing system: If the outer layer of your AR/FR system has an arc rating greater than the incident energy, or meets the necessary PPE category arc rating criteria, your AR/FR system is appropriate for that task—with or without natural, non-melting fiber base layers. Remember, the outermost layer of the system must be arc-rated and flame-resistant. Non-FR outer layers will likely ignite and continue to burn once the arc flash event is over, and an AR/FR base layer will be of little help as the flammable outer layer continues to burn.
- Multiple AR/FR layers: If a combination of AR/FR layers is needed to achieve a higher level of arc flash protection, the arc rating for the complete layered clothing system needs to be tested via ASTM F-1959 in a qualified lab.
Contrary to belief, you cannot simply “add” the layers together to arrive at the combined arc rating. For example, an 8 cal/cm2 shirt and 12 cal/cm2 jacket does not necessarily translate to a 20 cal/cm2 total system arc rating. The arc thermal performance value (ATPV) or the Energy Breakopen Threshold (EBT), which are types of arc ratings, must be determined in accordance with the ASTM F-1959 test method. If your layered system has not been formally tested with this protocol, then the highest arc rating of the individual garment layers determines the total system arc rating according to NFPA 70E.
When looking to assess the total arc rating of an AR/FR system, you may be able to reference manufacturer reports. ASTM F-1959 is a standardized fabric test method, and often either the fabric or garment manufacturers can provide layered system test results to confirm the combined arc rating of multiple AR/FR pieces. If the layered system in question has not yet been determined, then you can ask the manufacturer to perform the test at a qualified arc rating test laboratory.
AR/FR PPE must be worn, and worn properly, to achieve maximum protection. That is why promoting a want-to-wear experience is important, as it encourages even the most seasoned workers to arm themselves with trusted protection. Advances in AR/FR fabric technology go a long way to creating AR/FR base layer garments that enhance comfort and performance—and workers of all ages in daily wear programs benefit greatly from these improvements.
Regardless of the temperature, base layers can play a role in comfort. In cold weather, base layers provide additional warmth, while wicking moisture away from the skin during strenuous tasks to keep the worker dry. In hot and humid environments, the latest AR/FR base layers help moderate body temperature by incorporating specialty fabric blends that increase both breathability and moisture-wicking capabilities. These performance-driven fabrics draw away moisture—reducing sweaty discomfort, increasing air permeability, and decreasing trapped heat that can impact a body’s ability to regulate temperature.
This is just one of the ways base layers made with innovative AR/FR fabric blends can enhance the overall wear experience. Indeed, giving due consideration to wear experience, such as tailoring garments to the job site environment or to the task itself, helps further the use of daily wear PPE. AR/FR base layers, as with all daily wear garments, no longer need to bear the hallmarks of stiff, uncomfortable work clothing.
Base layers, when used in the context of an overall garment system, is one tool that can help encourage workers to wear their AR/FR daily wear. Daily wear PPE may also help remind workers to don other task-based PPE, like gloves and headgear, when specific tasks demand the added protection. If the clothing system fits well, is comfortable and does not detract from their ability to perform their jobs, workers are far more likely to be wearing all of their PPE gear should an arc flash incident occur. Reviewing your AR/FR garment requirements provides an opportunity to see if a base layer can play a role in furthering your overall protection system.
This article originally appeared in the September 2019 issue of Occupational Health & Safety.