Minimum Efficiency Reporting Value (MERV) is an industry standard that measures the overall effectiveness of air filters. Established in 1987 by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), the MERV is the only standardized filter classification system. It indicates the ability of a filter to capture larger particles between 0.3 and 10 microns (µm). As the MERV rating increases, the finer the filtration becomes.
MERV 8-rated filters can trap pollen, dust, lint, dust mites, mold, and other large particle impurities. Based on these characteristics, a MERV 8 is considered a superior filter compared to air filters with a lower MERV rating. But is filtration enough? In many cases, a MERV 8 air filter is more than adequate. However, if you're concerned about outdoor air pollution, have family members with respiratory problems, or pets at home, then opting for a higher MERV rating might be a good idea. MERV 1 to 4 are effective for controlling larger particles such as sanding dust, spray paint dust, lint and carpet fibers. Meanwhile, MERV 9 to 12 are effective for controlling humidifier dust, lead dust, vehicle emissions and welding fumes.
Most newer systems have no problem working with higher MERV filters. MERV 8 filters are suitable for most homes. However, people with respiratory problems, several pets or who live near sources of outdoor air pollution should consider replacing them with a MERV 11 filter. This comparison chart helps highlight the differences between MERV 8 and MERV 11 filters to make it easier to decide which one will work best. If you're concerned about the effects of inhaling fine air particles, that's another reason to choose a MERV 11 air filter over a MERV 8 air filter. Meanwhile, air filters with a MERV 14 rating or higher are designed for commercial HVAC systems that can withstand the coarser filter material. Choosing the right MERV rating is an important decision in terms of total cost, air quality and product durability.
Generally speaking, anything under a MERV 13 air filter should provide very efficient air purification in a home without affecting airflow.