An air compression system for supplying a compressed air into a pneumatically operated tool. The system includes an air compressor and air accumulator connected to the compressor and having a first accumulator and a second accumulators separate therefrom. A relief valve is connected between the first and second accumulators for allowing the compressed air to flow from the first accumulator to the second accumulator when a pressure of the compressed air accumulated in the first accumulator increases to a predetermined pressure. A check valve is provided between the first and second accumulators and in parallel to the relief valve for allowing the compressed air to flow from the second accumulator to the first accumulator. The accumulator is connected to the pneumatically operated too. If the tool requires small amount of compressed air for operation, the compressed air supply into the first accumulator is only necessary to reduce recharging period.