When it comes to air quality, higher MERV ratings are the most effective. However, they can also cause damage to your HVAC system. MERV 5 to 8 filters provide good filtration and can remove most pollen, mold spores, and dust mites. According to the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE), this type of filtration helps to create a healthier indoor air quality.
The key to better filtration against pressure drop lies in obtaining the highest pleat per foot, but newer filter designs have fewer airflow problems with higher MERV ratings. In short, the higher the MERV rating, the better the air filtration capabilities of a particular filter. MERV ratings range from 1 to 20, with 1 being the lowest level of filtration and 20 being the highest. Some air filters, especially those with higher MERV ratings, may reduce airflow due to improved air filtration.
These filters offer the highest level of filtration and are generally not necessary in most homes and businesses. If your HVAC system uses a coarser filter (usually in the 4 to 5 inch range, and typically mounted on the air handler), it's likely designed specifically for medium efficiency MERV filtration. It brings expert knowledge of a wide range of home air filtration topics, including HVAC filters, filtration efficiency, and indoor air quality.