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Resources > Flame Resistant Clothing Information
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Layering FR Clothing to Meet Requirements
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Changes to NESC and OSHA references to NFPA 70E in citations have prompted more construction companies and utilities to perform arc flash hazard assessments. These hazard assessments will result in an arc rating that indicates the  necessary level of protection. Many hazard assessment results and NESC are recommending an arc rating of 12 cal/cm². Most flame resistant shirt fabrics on the market today will not achieve 12 cal/cm² as a single, lightweight layer. If an employee required to wear FR clothing has to work in a high-heat environment or hot climate, it is extremely uncomfortable. Comfort and higher arc ratings can be achieved through layering.
Per NFPA 70E, layering is acceptable as long as the base layer, or layer closest to the skin, is of a non-melting fiber. However, per the 2009 edition of NFPA 70E, this non-melting, flammable layer, often 100% cotton, can no longer be considered part of the total arc rating achieved by layering. That said, what are your options for keeping employees protected and cool?
In the sports world, there has been an evolution in clothing called ‘Performance Wear’. This is often a close-fitting garment that wicks sweat away from an athlete’s body and provides odor elimination. This same clothing concept has been introduced to the flame resistant clothing market: a flame resistant performance wear base layer that provides moisture wicking and odor management. This performance wear is arc rated, but very low – as it is not meant to be worn as a single layer. However, when layered with other flame resistant garments, the arc ratings see a significant increase. See the data below:
6.25 oz FR Pro-C Knit Henley over FR Performance Wear = Arc rating Ebt 17.4 cal/cm2 in combination
7.0 oz. Indura® Ultra Soft® button front shirt over FR Performance Wear = Arc rating ATPV 15.2 cal/cm2 in combination
1. Products manufactured by National Safety Apparel and sold by FRSafety.com.
2. Arc rating was calculated in accordance with ASTM 1959-05. Tests Conducted at Kinectrics High Current Laboratory Toronto, Ontario, Canada.
 If the arc rating was calculated as a result of adding only the existing ATPV’s of each product, the total ATPV would be lower. The increased ATPV is attributed to an additional air barrier between the two garments. This concept has been used in the fire industry for many years, where turnout gear is multiple layers and multiple air barriers. As higher arc ratings are required, it is only natural that the safety industry should layer garments to achieve these higher ATPVs. Layering a flame resistant shirt over a flame resistant Performance Wear will provide a cool alternative and meet the necessary arc rating. Be sure when layering, that claims of higher ATPV’s are backed up by manufacturer testing.
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