Workplace Solutions Arc flash Protective clothing

Terms and acronyms of protective apparel

What are the common terms of protective apparel, and what do they mean?

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Responding is Scott Francis, technical sales manager, Westex: A Milliken Brand, Chicago.

Whether you’ve been procuring protective apparel for years or you’re new to the industry, one thing is consistent: Evaluating fabric and apparel options can feel like sitting in a bowl of alphabet soup. From fabric characteristics and features to standards and testing, the procurement process seems to have an acronym for everything. To help you waste less time Googling the meaning of certain terms and acronyms, as well as streamline the process of perfecting your picks, the following is a breakdown of common terms to master.

Flame resistant

Arguably the most important acronym to understand is also one of the most visible – FR. When a garment is classified as FR, it’s flame resistant – not flame retardant, as a flame-retardant chemical is used to impart the flame-resistance. A flame-resistant fabric has the propensity not to burn – making flame resistance an intrinsic property of the material – and will self-extinguish once the thermal source is removed. Self-extinguishing fabric is the key lifesaving feature of a fabric because it doesn’t act as fuel and reduces the time in the thermal exposure, mitigating body burn injury. Once you know that a garment is flame resistant, it’s critical to understand what thermal hazard standard its performance meets, as several standards exist that cover various thermal hazards.

Arc rating

The arc rating is the insulative property of a material – how well does it insulate to protect against a second-degree burn through the fabric or prevent fabric break open? Keep in mind that all arc-rated (AR) fabrics are flame resistant, but not all FR fabrics are arc-rated.

The better term for arc-rated clothing is flame resistant, arc-rated clothing (FR/AR). “Flame resistant” describes the key self-extinguishing characteristic and arc-rating – the insulative performance. Two types of arc ratings exist for a fabric or layered fabric system: ATPV and EBT.
ATPV: Arc thermal performance value is incident energy (cal/cm2) that results in a 50% probability that sufficient heat transfer through the fabric is predicted to cause the onset of a second-degree burn based on the Stoll Curve.
EBT: Energy to break-open threshold is the incident energy (cal/cm2) on a material that results in a 50% probability of break open. “Break open” is defined as any open area at least 0.5 square inches.

Neither ATPV nor EBT is better than the other. In fact, fabric manufacturers will determine both ATPV and EBT values and report only the lower, more conservative of the two numbers. Typically, knit fabric arc ratings are reported as an EBT, and woven fabrics are usually reported as an ATPV. Knits tend to be more insulative with less tensile strength compared with woven fabrics, so they can break open, hence the EBT arc rating. Woven fabrics have more tensile strength and are less insulative than knits, so heat transfers through the fabric without breaking it open, giving rise to an ATPV arc rating.

Although industry jargon can seem confusing, remember, the selection process isn’t an individual sport. Always lean on fabric manufacturers and apparel brands to help you navigate the sea of standards, features and, yes, acronyms.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.

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