When heating filters become clogged, they will cut down on a heating system’s efficiency and, over time, potentially cause other parts to wear out. The filters in your heating unit should be cleaned or replaced according to manufacturers specifications. In particular disposable filters should be checked, and changed as required, on a monthly basis, particularly during winter season.
The heating filter is located behind the door or panel that conceals the blower. With any luck the door is marked “filter”. Remove this door and you should see the filter. Carefully slide the filter out along its track.
Your local hardware store will have the necessary replacement filters for your heating unit. Buy the replacement, and slide it back into place. There should be arrows on the side of the filter to indicate the proper way to face the filter.