Forced air heating and cooling systems such as a heat pump or a central air conditioning system combined with a furnace are equipped with a furnace filter or air filter to reduce airborne contaminants and to help keep the heat exchanger and coil free of dust, dirt and debris. Most homeowners know to change the filter regularly, but you can improve indoor air quality and provide an added measure of protection for your system by upgrading to a high efficiency furnace filter.
The standard blue fiberglass filters that most HVAC systems are equipped with do a good job of collecting large particles of dust and hair, but a lot of smaller particle easily pass through these filters. Medium and high efficiency filters do a much better job of capturing smaller airborne particles. These filters are pleated and can be purchased through your HVAC contractor or at your local home improvement center.
Furnace filters are rated based on their ability to capture small particles. The higher the minimum efficiency reporting value (MERV), the better job the filter will do in capturing small particles. Standard filters have very low MERV ratings, but pleated filters are made with a range of MERV ratings from medium efficiency to ultra-high efficiency. Before you rush out and buy the filter with the highest MERV rating you can find, keep in mind that these filters also restrict air flow.
Filter manufacturers claim that the airflow restriction is not significant, but an older system could be negatively affected by installation of an air filter with a very high MERV rating. Try using a medium efficiency filter first. If your system can move air through a medium efficiency filter without a problem, then you could consider a further upgrade. Remember to check the filter frequently and change it whenever it gets dirty.
