Air or nitrogen is compressed in a single-stage pump using the standard operating cycle of a piston compressor. Compression starts at a low pressure moving through the joint work of the inlet and outlet solenoid valves. The compressed air or nitrogen then enters the booster where it is further compressed up to 40 bar, in a single stage. The inlet pressure switch stops the booster when the inlet pressure exceeds the maximum allowed value or drops below the minimum allowed value. Cooling is provided by the axial fan installed on the shaft of the booster. The booster is lubricated by the oil in the crankcase. The crankcase is vented via the oil separator and the oil breather, which allows operation with minimum oil carryover.