Clogged heating filters will impair heating systems efficiency, particularly over time. It can also cause other parts to prematurely wear out. Heating unit filters should be cleaned or replaced on a regular basis. In particular disposable filters should be checked often, we think once a month, and changed out as required. This is particularly important during the winter time.
There is a door which is typically marked “filter”. And it covers the blower and also the filter. Take the door off and you should see the filter. It’s usually has its own track and you can slide it out carefully.
Bring this older filter down to your nearby hardware store and they will have a replacement for you. As you put the new filter back, make sure you have the follow the arrows on the filter which will tell you which to face the filter, when you put it back.