Potential impacts of ultra-high-pressure (UHP) technology on NFPA Standard 403

Ultra-high-pressure (UHP) technology as well as compressed air foam (CAF) and combined agent firefighting systems (CAFFS) have proven to enhance the performance of firefighting equipment using water and aqueous film forming foam (AFFF). UHP systems are capable of producing small water droplets at high velocity. As droplet size is reduced, surface area relative to mass increases, improving heat transfer. Smaller droplets however, experience greater drag, reducing throw distance. Findings indicate that on average, 150 m/s exit plane velocities result in maximum throw distances of between 4600 and 5600 orifice diameters. UHP prototype and full-scale testing conducted from 2004 to 2006 found that exit plane velocities of 150 m/s were found to produce 90–100 μm droplets, sizes considered optimal for fire extinguishment. In addition, UHP systems were able to extinguish two-dimensional fuel fires ranging in area from 81.6 to 613.8 m2 using one-third the agent when compared to baseline AFFF tests, and one-tenth the NFPA 403 standard.