The present invention relates to a compressor (1) that has an associated coolant circulation system (1, 4, 6, 8, 11, 13), and also to a method of maintaining a low bacteria content in the coolant circulating system (1, 4, 6, 8, 11, 13), in which method gas and coolant are supplied to the compressor (1) during running of the system and the gas is compressed in the compressor (1) to an outlet pressure, the gas and the coolant are removed together from the compressor (1) and then separated into a respective gas and a liquid phase, whereafter the gas is passed to a recipient and the liquid is cooled before being returned to the compressor as coolant. The method is characterized by creating bacteria-killing conditions intermittently in the system by appropriating the heat-generating capacity of the compressor (1) to raise the temperature of the circulating coolant to at least 55° C. for a duration of at least 15 seconds.