The piston air compressor can be divided into the following categories according to the size of the air discharge: Air compressor exhaust refers to the suction state of free gas flow. General provisions: the shaft power < 15KW, exhaust pressure < 1.4mpa for the micro air compressor. Small air compressor 1m3 / min < exhaust volume < 10m3 / min Medium air compressor 10m3 / min < exhaust volume < 100m3 / min Large air compressor exhaust capacity > 100m3 / min.