Arc Flash

The Fabric Matters: Flame Resistant Specification Considerations

The first thing specified by a significant majority of people is the flame resistant (FR) or arc rated (AR)* fabric brand. Read the top six reasons whysafety directors cite fabric being the top factor in selecting

The first thing specified by a significant majority of people is the flame resistant (FR) or arc rated (AR)* fabric brand. The number, type and source of these fabrics has expanded dramatically in the last few years, and there have been significant failures, making it more critical than ever to thoroughly research and select trusted, market-proven brands. The fabric choice is the biggest single decision for a lot of reasons, not least of which is that there are huge differences in protective performance, FR durability, comfort, shrinkage and value. These differences exist not just across fiber types (natural, synthetic, or blends), but also within fiber types (ie FR cotton blends).
Compliance is important, but it is only a minimum bar, not a guarantee; therefore, companies should never allow compliance alone to guide their choices. It is important to research a list of properties, especially track record, before making a decision.

Safety directors cite a number or reasons why they answer the fabric question first:


Protection
Protective performance ratings (ATPV, or Arc Rating; NFPA 2112, or flash fire rating; etc) are based entirely on the FR fabric. We don’t get a rating on a blue shirt or a red coverall; the protective designations are fabric brand and weight specific. All single-layer garments made of that particular brand and weight of fabric will then carry that rating, regardless of garment type, manufacturer, color, and so on. Protection is, of course, the reason PPE exists and the title of the category, so it is completely understandable that this property is a primary driver when selecting preferred FR and AR fabrics.


FR Durability
The protective performance tests are excellent, and the ratings are highly reliable and relevant to the hazards they address, but they do not prove long term durability of flame resistance. The arc rating test (ASTM F-1959) uses fabric samples washed 3 times and dried once. ASTM F-1506 is often the next thing specified, because it requires FR durability through 25 launderings. However, this represents about 6 months to a year of use, while most FR garments are expected to be in service 2-5 years, leaving a significant gap between existing arc flash standard FR durability and actual field use.
Many people look to NFPA 2112 to fill this gap, because one of the 2112 requirements measures flame resistance after 100 industrial launderings. While this may seem sufficient at first glance, there are two issues to consider. First, the wash method in the standard uses perfect water chemistry, temperatures, detergents, load levels, operator skills, etc. Real world laundering is often much more aggressive, and potentially detrimental to some FR technologies. Second, fabrics are submitted for testing by the manufacturer, who, if so inclined, can carefully walk a specific sample through a scaled process to achieve a desired test result. However, the tested sample may bear very little resemblance to what is being produced in full commercial scale months or years later.

The standards are minimum compliance bars, broadly written and intended to be inclusive, not exclusive. This is why so many safety managers insist on established, market-proven brands. Market proof is not based on de minimus standards, or marketing spin, or sales claims. Market proof is when the industry votes, over time, with its wallet; in other words, a product is specified, serves its purpose well, and when replacement is necessary years later, the same product is selected again and again. Valued characteristics are not limited to protection; several other more basic garment traits are very important as well.


Shrinkage
A bargain fabric is no bargain at all if it has to be removed from service prematurely because it no longer fits due to excessive laundry shrinkage. It can also become a safety hazard if it is not worn, or is improperly worn because it is too small. Almost everything shrinks somewhat in laundering, but some fabrics shrink both more rapidly and more excessively; low price is often an excellent indication of products with significant shrinkage problems. This is because quality preshrinking of FR fabrics is both very difficult and expensive.

It is difficult because many FR technologies can achieve either good FR durability to laundering or reasonable shrinkage control, but not both. There are very few processes which are able to achieve FR durability for the life of the garment, and excellent shrinkage control. This control is achieved by compaction of the fabric at the end of the process. To understand why this is expensive, picture a machine in which, for every 100 yards of fabric that enters, only about 90 yards exits, reducing salable inventory by 10%. This technology allows the manufacturer to take the hit on the shrinkage cost, so the end user does not.

Cost
While FR fabrics vary widely in price, they represent, on average, over half the initial cost of a finished FR garment. Since the fabric is the largest cost component, it makes sense to carefully consider the options and performance characteristics. And performance isn’t limited to protection; there are significant life cycle cost implications with other fabric brand properties such as shrinkage, FR durability and fabric durability. Purchase price is the most obvious point of comparison, but market-proven performance in use should weigh heavily in the decision as well.

Comfort
Comfort is an inherently subjective property, and is very hard to quantify. There are a few definitive knowns: cotton and cotton-rich blends are perceived as more comfortable; lightest weight does not mean greatest comfort, particularly when the lighter fabric does not absorb sweat (such as when comparing synthetics to natural fibers), and the largest components of comfort other than fit are fabric brand dependent. Fabric brand qualities like softness (new and over time), breathability, moisture management, drape, etc have a major impact on the comfort of the wearer.

As with shrinkage, cost is often an excellent barometer of comfort as well, because for many technologies, FR durability and softness are at odds. Only a very few brands manage both, and these tend to be more expensive because the necessary processes and equipment are expensive.

Appearance
Garment appearance over time is not important to everyone, but in many cases FR garments are also considered to be uniforms, and thus a part of a company’s public image. No one wants to remove garments from service early because a red shirt turned pink or blue coveralls faded to gray. Less expensive dyes result in less expensive garments, but at the cost of poor color retention through laundering or UV. In addition, stiff fabrics can lead to streaks or “chalking” in darker colors because of abrasion at garment stress points. This negatively impacts the appearance and can substantially reduce the garment wear life.

These differences can be quite significant across fabric categories (i.e. aramids vs. FR cottons ), but many people are surprised to learn there are also major differences within a fabric category (i.e. one FR cotton brand vs. another).

Conclusion
It’s easy to see why most safety professionals rate the FR fabric brand as the first and most critical decision in program implementation: the fabric is the key component of protective rating, durability of flame resistance, shrinkage, comfort, cost and long term appearance. They also recognize that there are major protective and life cycle cost differences from one fabric brand to another, even within functionally similar catagories. And since the standards are a minimum bar, they do not obviate the need for research. There is simply no substitute for a thorough understanding of relevant FR and AR fabric performance characteristics and market-proven performance before specifying preferred brands.

*”arc rated” is a new designation in the 2012 NFPA 70E standard; the nomenclature is intended to drive consumers to recognize that while all arc rated fabrics are FR, not all FR fabrics are

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