Page 36 - Occupational Health & Safety, May 2019

PROTECTIVE APPAREL
Inherent fibers offer a solid layer of FR protection.
Non-inherent fibers gain flame retardancy from a chemical coating.
lab environment can never perfectly replicate the real world.
One shortcoming of the certification process is consideration for how FR clothing might perform in motion (the wearer moving to safety) after exposure to heat, flame, or fire. Manufacturers of FR workwear hope that their products are never needed for a fire emergency; however, if they are needed, they must provide con- tinuous protection until the wearer can escape from the hazard. This means an FR garment needs to stay intact and flexible so an
accident victim can maintain mobility and protection.
A very effective method of flame retardancy used with treated cotton, cotton blends, or other plant-based fabrics converts the or- ganic material in the fabric to a carbon char. This chemical process absorbs heat; releases carbon dioxide and water; makes the cotton unavailable as a fuel; and the char blocks heat from the body, all of which provide protection in a thermal emergency. One down- side to this process is that this chemical reaction is exothermic or produces heat, which can add to the burn injury. Another prob- lem is that the formed carbon char is brittle and does not have the strength or integrity of the original fabric. Even slight motion after exposure can cause the fabric to flake and disintegrate. Inherent fibers can withstand higher temperatures and greater levels of heat energy before physical changes take place, allowing the fabric to
stay stronger and flexible for longer.
This structural integrity after heat or flame exposure is not re-
flected in a certification test report and can be seen only by witness- ing an actual exposure. Tests have been conducted to gauge the lev- el of fabric integrity and flexibility remaining in fabrics after testing using the industry standard thermal manikin test ASTM F1930.
As shown in these photos, the test manikin was dressed in a 7 oz/yd2 non-inherent FRT 88/12 cotton/nylon blend shirt paired with 6 oz/yd2 inherent pants. Both garments were received new and then washed and dried in one home laundering cycle using AATCC 135 industry recommended wash and dry procedures.
The clothing was exposed to test standard 2 calories/cm2 of heat
Non-inherent shirt after test burn.
Test manikin before exposure, dressed in non-inherent shirt and inherent pants.
Inherent pants after test burn.
32 Occupational Health & Safety | MAY 2019
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Inherent pants after test burn showing pliability post-burn.
energy for three seconds. Both the shirt and pants that were tested are commercially available certified garments. Test data shows that both garments would be well below the maximum total predicted burn injury (TPBI) percent required for a certified garment.
After exposure, the garments were very carefully removed from the test manikin to minimize damage to the fabrics. What the test
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