The caution that the NFPA 70E-2000 standard focuses on the thermal component of arc flash is overlooked by many safety managers. It is common to incorrectly judge a garment’s arc flash protective capability on its flash fire thermal performance.
The differences between electric arc flash and flash fire must be considered when selecting arc flash protective apparel in that some of the requirements for flash fire protection that are taken as a “given” do not necessarily apply to arc flash protection.
Traditional woven fabrics used in flash fire protection have one significant limitation. They are designed for daily use in end uses where the risk of a flash fire is ever present. Fabric durability and laundering requirements dictate the use of such woven fabrics. This may not appear to be a significant issue when garment durability equates to lower cost per use and is environmentally sound. However, the mechanical processes involved in producing a woven fabric allow for only limited variability in fabric density. Density is more important in arc flash protection because the thermal energy released is almost entirely radiant and the event duration is very short. As a result, the thermal energy dissipates quickly in air.
Pyrolon® DTP represents a significant departure from the conventional approach to arc flash protective garments. The nonwoven fabric weighs 204 g/m² and is four times the thickness of woven thermally protective fabrics. The unique material provides an ATPV (arc thermal protective value) of 14.3 cal/cm² - some 2.5 times that of aramids and 1.8 times FR cotton.
Lack of durability limits a nonwoven products appeal to areas with a high risk of garment contamination or damage. In arc flash protection however, the durability requirement is different. NFPA 70E-2000 validates layering garments to meet protection requirements as arc flash hazards increase. Workers may add FR clothing layers as the need for protection occurs making use of additional layers of FR clothing only when needed. In short, because of the nature of electric arc flash, workers are exposed to the hazard for much shorter periods of time than are many workers in potential flash fire environments, thus the requirement for product durability is considerably less.
It needs to be recognized that arc flash is different from flash fire and that the differences can have a significant impact on conventional wisdom where protective apparel is concerned. Consideration of nonwoven garments like Pyrolon® DTP can benefit a company’s bottom line by reducing both garment costs and the threat to workers health.