Most air tools are designed to operate efficiently at 90 PSI. Pressurized air above 90 PSI in the air tank is additional useful tool operating air (useful air). As the air tank pressure falls below 90 PSI, the tool user must stop and allow the air compressor pump to repressurize the air tank (recover). This Porter-Cable pancake compressor has a maximum pressure of 150 PSI,resulting in 60 PSI of available useful air prior to recharging when using a 90 PSI tool. This results in 71% longer tool operation!