To make best use of compressed air in a tank and to use pneumatic tools safely in a system connecting a low-pressure pneumatic tool and a high- pressure pneumatic tool to a tank of one compressor.

This system is equipped with a means to store 10-30 kg/cm2 compressed air in the air tank, a first and a second outlets of the air tank, and a first pneumatic tool driven by low pressure compressed air, a first pressure reducing valve mounted to the first outlet for supplying 7-10 kg/cm2 or less compressed air to the first pneumatic tool, a second pneumatic tool driven by high pressure compressed air, a second pressure reducing valve mounted to the second outlet for supplying 10-30 kg/cm2 or less compressed air to the second pneumatic tool, a first hose for connecting the first pneumatic tool to the first pressure reducing valve, and a second hose for connecting the second pneumatic tool to the second pressure reducing valve. A joint of the first hose and that of the second hose are not interchangeable.