Replacing a gas furnace filter is a very simple task and one that should be one on a regular basis.

What Does the Filter Do?
The filter is designed to clean the air that is drawn into the combustion chamber to mix with the gas. The air drawn into the filter will contain dust and particles that could affect the clean burning of the fuel-air mixture.

Obtain the Right Size Filter
The filter compartment is usually clearly marked and easy to access without special tools. Look at the old filter to find the size that is printed on it or look in your furnace handbook for the specs. Filters are available from hardware stores.

Changing the Filter
It isn’t necessary to turn off the boiler while you are changing the filter but it is easier if the boiler is not running so you don’t have to contend with the forced draft. Make sure that you check the direction of airflow that is indicted by the arrows on the filter.

Filters should be changed regularly and the furnace hand book will tell you the interval between changes. It is a good idea to have a calendar or a chalkboard near the furnace so you can make a note of the due date of the next change.