UNDER LAYER DO’S AND DON’TS
Most single layer FR garments are designed to protect against specific hazards without the need for additional under layers like a T shirt. However many workers prefer to wear a T shirt for comfort reasons. So what are the safety implications of doing this?
UNDER GARMENT DO’S
Wearing a T shirt or any other type of under garment under your FR coverall, pant or shirt can be beneficially in a number ways. First and foremost it can add to the protection level. Having an additional layer of fabric between your skin and the thermal exposure, whether it’s flame resistant or not can improve the protection level from electric arc flash, flash fire or other short duration thermal exposures. The fabric itself increases the amount of barrier plus the added air gap between the outer FR garment and the T shirt adds to the insulation against the heat. Secondly the T shirt can add to the comfort as it is made to be next to the skin and is typically softer to the touch. And lastly some T shirt materials have the ability to absorb perspiration better than FR fabrics. This last benefit can be either a pus or a minus depending on whether the fabric dries quickly or stays wet, but that’s another topic all together.
CAUTION: Before you put on that T shirt there are some under garment don’ts you need to be aware of.
UNDER GARMENT DON’TS
As stated above, wearing a T shirt under an FR garment has benefits, but you need to be careful with the type of T shirt or other under garment you wear. In a short duration thermal exposure there will be a certain amount of thermal energy/heat that passes through the outer single layer FR garment. This thermal energy can be enough to produce varying degrees of skin burn injury with or without a T shirt and it can also impact the T shirt material. There can be enough thermal energy to melt a T shirt made from synthetic materials like acetate, acrylic, nylon, polyester, polypropylene or others. The melting of these materials when in contact with the skin can significantly aggravate the burn injury. Also, if that non-flame-resistant under garment is not fully covered, by the FR outer layer, it can ignite and burn causing additional burn injury. There are various OSHA rules and industry standards that specifically spell this out.
OSHA 29 CFR 1910.269 Electric Power Generation, Transmission, and Distribution:
Section (l)(6)(iii) “Note: Clothing made from the following types of fabric, either alone or in blends, is prohibited by this paragraph, unless the employer can demonstrate that the fabric has been treated to withstand the conditions that may be encountered or that the clothing is worn in such a manner as to eliminate the hazard involved: acetate, nylon, polyester, rayon.”
NFPA 70E Standard for Electrical Safety in the Workplace:
Section 130.7(9)(c) “Underlayers. Meltable fibers such as acetate, nylon, polyester, polypropylene, and spandex shall not be permitted in fabric underlayers (underwear) next to the skin. Exception: An incidental amount of elastic used on non-melting fabric underwear or socks shall be permitted.”
Section 130.7(11) “Clothing consisting of fabric, zipper tapes, and findings made from flammable synthetic materials that melt at temperatures below 315°C (600°F), such as acetate, acrylic, nylon, polyester, polyethylene, polypropylene, and spandex, either alone or in blend, shall not be used. Exception: Fiber blends that contain materials that melt, such as acetate, acrylic, nylon … shall be permitted if such blends in fabrics meet the requirements of ASTM F1506 … and if such blends in fabrics do not exhibit evidence of a melting and sticking hazard during arc testing…
NFPA 2113 Standard on Selection, Care, Use, and Maintenance of Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire:
Section A.5.1.8 “Undergarments should be melt-resistant. Certain synthetics or synthetic blends worn as undergarments can be inappropriate for use under flame-resistant garments, since the transfer heat could cause them to melt. Undergarments with melt-resistant properties are recommended (e.g., cotton, aramid, wool).”
NESC C2-2012 National Electrical Safety Code
Section 410 A(3) “If the assessment determines a potential employee exposure, clothing made from acetate, nylon, polyester, or polypropylene shall not be worn, unless arc rated.”
The bottom line is, wearing an under layer beneath your FR garment can add to the level of protection as long as it doesn’t ignite or melt. Read the standards associated with your industry or hazard to determine your specific needs and only wear those under garments that won’t add to the wearers burn injury should they be exposed to a thermal hazard.
Mark Saner – Technical Manager
Workrite Uniform Company
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