Ask an Expert: Changing Furnace Filters
Updated: Sep 26
Regular air filter changes should be part of your home maintenance program.
How often should I change my furnace filter and what types are available?
To check an air filter, turn your heating or cooling system off at the thermostat and pull the filter out. Hold it up to a light source or tap one edge on the floor. If you see significant buildup of dust or dirt, it's time to put that filter to rest.
Regular air filter changes should be part of your home maintenance program to maintain healthy indoor air quality and to keep your heating and cooling systems running at peak efficiency. Change your filter every three months or according to manufacturer's recommendations. When replacing a filter, pay attention to the recommended airflow direction typically indicated by a printed arrow on the side of the filter.
There are several types of disposable air filters available. Panel filters, consisting of tangled fiberglass strands, are the most common. These filters are low in price, but not very effective at filtering the air. More expensive pleated filters made with woven polyester or nonwoven spunbond material provide a larger filtering surface. Nonwovens can be electrostatically charged to improve particle capturing without decreasing airflow.
Replaceable pocket filters consist of parallel bags or "pockets" of thick polymer material arranged side-by-side with the pockets open to incoming air. The pockets make it difficult for dust, dirt, germs, and water droplets to pass through, but result in higher airflow resistance.
Deep rigid cell filter boxes (typically 4 inches thick) reduce fan energy consumption without hindering airflow. They also last longer than other types of filters. Another option is a permanent washable air filter that must be cleaned periodically to deliver the best possible filtration and optimal airflow.