The onset of winter can spell trouble for users of CPAP sleep apnea devices. During this period, heating systems (electric, gas, wood) come into operation, generally drying out the air in homes. In winter, it’s therefore important to review the adjustment of your humidity level provided by the humidification system on your CPAP machine. Generally, the level will be adjusted upwards slightly during the cold season, and then downwards again when spring temperatures return.