When it comes to Arc Flash protection, Volt Safety recommends, the use of Inherent FR Fabric. Inherent Fabrics such as DuPont Protera; Parvotex, Lenzing and Nomex do not lose their FR properties. Fabrics that are treated with FR sprays or have FR thread woven into a cotton base, lose their FR properties over time and should be replaced after 50 washes. This is not only difficult to monitor but costly to replace.