The topic of layering arc-rated apparel and its protection in comparison to other protective apparel is often a hot topic of discussion. There is currently not an industry standard or requirement we can point to that guides us with a preferred method to protect the worker against incident energies in this range. In fact, the well-recognized NFPA 70E Arc-Flash PPE Category tables point to both layered arc-rated apparel or an arc-flash suit as acceptable options.
Factors That Drive Safety Decisions
For both the employer and worker, the process to making the safety decision on selecting arc-rated apparel and PPE involves various considerations including the following influencers: hazard level, frequency of hazardous work through the workday or project, number workers affected, cost and compliance-risk drivers such as wearer comfort and ease of use. What also matters in safety purchasing decisions and trends is what industry is asking the question and what arc rating level needed.
The U.S. electrical utility industry most commonly uses arc-rated apparel in single and multi-layered apparel combinations because of the varied hazard levels in the work done daily, and the ever-changing weather conditions and temperature that affect the industry. Their multi-layered clothing combinations approach arc ratings in the 13 to 25 cal/cm², but layering options diminish substantially when nearing 20 cal/cm² requirements. In other applications such as substation work, utilities commonly use 20 to 25 cal arc flash suit PPE rather than prescribing multi-layered arc-rated clothing combinations that achieve the same arc ratings. By comparison, other industries such as electrical contractors and industrial workers do not prefer layered arc rating combinations but use arc flash suits for most situations where incident energies exceed 12 cal/cm².
The U.S. market is very definitive when selecting arc-rated apparel for situations up to 8 to 12 cal and at or above 25-cal exposures. Where the question about the effectiveness and safety of layered clothing or requiring same level protection in arc flash suits is most routinely asked is for tasks where the incident energy ranges 13 to 25 cal/cm².
For years, industrial companies have selected 8 to 12 cal arc rated shirts and pants and have not abandoned their original investment decisions to transition to arc-rated, task-based PPE kits for good reason. The on-going innovation in arc-rated protective fabric technologies continues to drive improved user comfort and conformity with lighter fabrics, that stretch, have a better appearance and quick-dry technologies that make daily wear apparel more acceptable than many of the best options available five to ten years ago.
More recently, added advancements that borrow from fabric technologies born in the U.S. military include “Phase-Change” materials that optimize cooling performance by helping moist movement but also store body energy to keep workers warmer in cool or frigid conditions. These multi-fiber blends deliver a significantly improved experience over the first generation of single or two fiber aramid or cotton blend AR/FR fabrics. The science includes fabrics that have hydrophilic fibers that wick and draw moisture away from the body in combination with hydrophobic fiber blends that push moisture out of the fabric to create a superior moisture managing system that dries quick and delivers cooling or warming functions at the fabric level of the garment.
Since these advancements are available in a variety of shirt, pant and seasonal outwear options, it appears that the market of current users of daily wear aren’t converting from protective clothing purchasing practices to personally assigned PPE kits any time soon. Also, expanded services by rental companies to provide customers with added PPE options to include innovative head and hand protective kits offered in conjunction with CAT2 arc-rated daily wear, further galvanizes long-term user commitments to arc-rated daily wear apparel for the majority of the industrial market for tasks at or less than 12 cal/cm².
The manufacturers of arc-rated task-based kits focus on electrical PPE solutions with arc ratings greater than 25 cal/cm². Most common users of task-based electrical PPE are electrical contractors that conduct on-going electrical maintenance, the construction industry and smaller workgroups in the electrical utility industry with exposure to higher incident energy in underground network, substation, and generation work environments. Typical usage is very brief to properly de-energize a circuit or enclosure prior to performing other tasks. This segment of the arc flash safety industry historically has been stagnant, lacking on-going innovation to improve the user experience. However, in the last five years, new arc flash PPE brands from reliable U.S. manufacturers focusing on resolving the age-old problems with uncomfortable and difficult to wear arc flash safety gear have revolutionized arc flash PPE.
New arc flash PPE has design advancements that include lightweight fabric systems and other user-friendly features such as improved mobility and airflow in head protection. These features, combined with design improvements, make it easier to put on and take off. These significant improvements to electrical PPE keep traditional users of task-based kits from changed spending or buying practices to move to arc rated daily wear.
Best Approach to Mid-Level Energy Ranges
With these technology advancements keeping users and buyers locked into CAT2 and 40 cal arc flash PPE, the question is what is the best overall approach for situations that fall into the middle, generally the rarer incident energy ranges of 13 - 25 cal/cm²? These are several of the many important considerations employers evaluate before making safety purchasing decisions on arc rated layered daily wear or arc flash PPE kit systems to cover this range of arc flash protective needs:
Are there protective differences in layered garments versus arc flash suits? No, we first need to rule out any questions or concerns about protective differences between AR/FR layered apparel compared to a two-layer arc flash suit manufactured with the same fabric combination. The ASTM F1959 test method (Standard test Method for Determining the Arc Rating of Materials for Clothing) is a method to determine the arc rating of material or a combination of materials. It is important to know that the test method does not test garments, but in a rigorous and standardized process is designed to calculate the arc rating of single or multilayer systems of FR layers.
As mentioned by Brian Shield, Service Line Manager for ArcWear, “Using an arc flash suit or layering independent garments are simply different means to the same end. Protection feel does not change based on the technique used to achieve it. For example, a 20-cal rating provides 20 cal protection, no matter how achieved.”
Head Protection. The head protection you select may influence the related decision to layer apparel or purchasing kits. Article 130.5(G) of the 2021 NFPA 70E limits balaclavas and face shields for head protection at 12 cal and requires an arc flash suit hood for exposures greater than 12 cal/cm2. Similarly, the NESC recognized by utilities, allows for shields and balaclavas to 20 cal/cm2. Since most employers want identical head and body protective levels for arc flash PPE, an arc flash suit ensemble would provide this consistency.
Available Layering Data. The manufacturers of arc-rated FR fabrics typically have single and combined layer arc ratings of exclusively their products available, but with the expanded choices of fabrics and arc rated apparel brands available today, many end users want information about competitive fabrics in layers. Since the arc testing lab time can be difficult to obtain, and fabric manufacturers have such diversity in their own portfolios, it is perceived to be difficult to find arc ratings for combined clothing brands. Many specific combination tests have been commissioned by the U.S. electrical utilities over recent years and often the garment manufacturers and distributors now have extensive arc ratings combinations of various fabric brands in layered systems, often in this range of 13 to 25 cal/cm² resolving this issue for everyone.
Risk of Human Error. We would all agree that following rules, instructions and procedures is easier if simple. The complexities of a safety strategy designed to allow more layering choices introduces new challenges to ensure all workers follow layering guidelines every time. With the extent of available base-layer, daily wear and over-garment layering options available, employers can find many combinations to exceed the maximum incident energy levels workers are expected to face. Mitigating the risk of human error is possible through on-going education about the purpose and functionality of layered AR/FR clothing, and monitoring use for accuracy.
Comfort and mobility. If the earlier considerations favor arc flash suit ensembles over layered daily wear systems for this range of exposures, the equalizing variable that matters most is the comfort and mobility experienced by the wearer.
The truth is, both approaches work very well, with comfort focused improvements in the market making either solution highly effective to deploy and monitor. The newest, lightweight “phase-changing” FR fabric technologies in layered apparel provide elevated levels of protection in conjunction with great comfort that workers actually like to wear as layered systems and will routinely wear correctly when required. Also, super-lightweight and enhanced 40-cal arc flash ensembles have recently appeared that are now lighter than ever. Some brands also now include added system design features making these suits easier to put on and take off, resulting in many employers prescribing the use of these ensembles for all various ranges of incident energies above the range of the arc rated daily wear apparel.