Method and apparatus for heating gases cooled by an aftercooler that receives hot gases from a compressor. The method includes the steps of directing at least a portion of said hot gases to means for bypassing the aftercooler, and using the bypass means to direct hot gases to a location that receives cooled gases from the aftercooler. The hot gases are used at the location to heat the cooled gases when ambient temperature is at or below freezing, and are used downstream from the aftercooler when moisture freezes in the aftercooler.