Page 32 - Occupational Health & Safety, May 2019

PROTECTIVE APPAREL
New Considerations for Selecting Flame-Resistant Workwear
In a real-world fire emergency, chances are that workers will need to flee to safety, so it is critical that FR workwear continue to provide coverage and allow mobility to protect workers after a flash fire or arc flash.
BY CAROLINE HOLTZMMAN
28 Occupational Health & Safety | MAY 2019
www.ohsonline.com
illions of people across the globe go to work each day in environments with a heat or fire hazard. For these workers, flame-resistant (FR) or flame-retardant
treated (FRT) protective garments are designed to provide a last line of protection against short-duration fires. Many different fibers can be used to make FR or FRT garments, each with their own advantages and disadvantages. With so many options, it can be dif- ficult to select the best product for each specific job function.
There is growing industry awareness about the im- portance of knowing how a garment will perform not only at the moment of heat or fire exposure, but in those vital seconds just after exposure when an em- ployee needs to escape from the emergency.
Safety Expert Shares Process
A highly regarded industry safety expert who speci- fies and selects garments for a Fortune 50 oil and gas company recently shared with me the process he uses for FR garment selection. Like most safety profession- als, he considers certification to key industry test stan- dards and published performance results as a mini- mum requirement.
He prefers to witness actual burn testing of the garments and analyzes the results for himself. But he doesn’t just stop there because he knows that the test methods simply establish minimums for performance and the live burn tests are conducted on a stationary manikin. As he explained, in the real world, a flash fire or arc flash is a dynamic event that either generates motion in the individual from the pressure wave or blast or from the worker’s reaction to protect himself as he flees from the event. That’s why he now consid- ers the state of the garment post burn as a mandatory part of the selection process.
Is the garment still intact so it continues to offer protection? Is it flexible enough that, in a moment of crisis, an employee still has mobility to quickly escape heat and flames? If the garment passes this test, he then relies on extended-duration field wear trials to confirm a garment’s durability, ease of cleaning, com- fort, fit, style, and buy-in from workers who will be wearing the garments on a daily basis.
The Difference is In the Fiber
What properties determine how a fabric will perform after exposure to a thermal event? The answer has to
do with the makeup of the fiber and fabric.
Fibers used for FR garments are either inherent or non-inherent. The term inherent is a scientific textiles term spelled out in the definitions sections of FR work- wear standards NFPA 2112, NFPA 1975, NFPA 1971, and Canadian standard CAN155.20. These North American industry standards define inherent flame resistance as “flame resistance that is derived from the
essential characteristics of the fiber or polymer.”1 Inherent fibers are made of substances or materials that are not flammable; do not support combustion in air; and do not provide fuel for a fire, either with or without an ignition source. The thermal protection of inherent fibers is permanently part of the fiber chem- istry and goes completely through each fiber strand— end to end, from the outer surface down to the core. The solid layer of fire resistance of inherent materials cannot be stripped off, washed out, or worn away, no matter how the garment is used or laundered. If the
fiber is still present, the FR protection is still there. Inherent fabrics:
■ are self-extinguishing in air
■ can withstand elevated temperatures for long
periods of time without degrading or changing
■ will not melt or drip when exposed to high
temperatures or fire
Commercially available inherent fibers used for
high-temperature garment applications include: me- ta-aramid, para-aramid, carbon, PBI (polybenzimid- azole), and PBO (polybenzoxazole).
Non-inherent fibers, which are flammable in their natural state, include: cotton, nylon, polyester, and fi- bers made from cellulosic plant materials such as ray- on, modal, or lyocell. When exposed to heat or flame, non-inherent fibers become fuel for the fire. To make a non-inherent material flame retardant, a chemical must be added to the mix before the fiber is spun in the production process, or a chemical must be applied to the outer surface after the fibers have been woven or knitted into a fabric.
Considerations Beyond Certification
The personal protective equipment (PPE) marketplace is full of commercially available FR workwear options certified to the two main North American thermal ap- parel standards: NFPA 2112-2018 and ASTM F1506- 2017. Fabrics, sewing thread, labels, and closures must pass multiple and rigorous test standards to achieve certification. But it is important to remember that a