Winter is a good time to do a little property maintenance on the inside of the home. The grill protectors on your fans need to be kept clear of dust and spider webs in order to function efficiently. Vacuum around the fire / smoke detectors and the bathroom fans. Vacuum the radiator grills on the back of your refrigerator and freezer. Empty and clean the drip trays.
If you have a humidifier you should clean the reservoir with an anti-bacterial solution periodically. The medium (used to hold water - usually a pad, filter, screen or a mesh) should be replaced regularly.
If you have a de-humidifier you should change the filter at least once a year. In some units, you can clean the internal filters. Keep the water container emptied and cleaned to prevent the growth of mold and mildew.