What Types of Particles Can Be Filtered Out By Different Air Filters With Different MERV Ratings?

The Minimum Efficiency Reporting Value (MERV) rating of an air filter is a measure of how effectively it prevents dust and other contaminants from passing through the filter and entering the air stream.

MERV indices range from

1 to 20, with higher MERV indices trapping small particles more effectively than filters with lower MERV indices. A filter with a MERV rating of between 1 and 6 can remove particles between 0.3 and 10 microns with an efficiency of 20%. It can remove small particles such as dust mites, spray paint dust, carpet fibers, and pollen.

If you're concerned about the effects of inhaling fine air particles, then you should opt for a MERV 11 air filter over a MERV 8 air filter. Fine air particles measure 2.5 microns or less, and at that size they can enter lung tissue and enter the bloodstream. MERV 11 air filters can filter a large percentage of fine particles, but a MERV 8 air filter cannot. As the MERV classification system is standard, it makes it easier to compare filters with different MERV ratings.

The MERV leaderboard below shows how the MERV 8 and MERV 11 filters compare. Air filters with a MERV rating between one and four offer the least protection, with an efficiency against dust spots of 20% or less. These filters help keep the system clean by filtering out particles that can damage the coils and reduce efficiency, such as dust mites, pollen, and other fibers. If budget is a more important concern than health, these are the filters for you.

MERV indices are determined based on the effectiveness of a filter to filter particles of different sizes. Specifically, we are talking about 12 particles of different sizes, from 0.3 to 10 micrometers (µm) in diameter, that were created in a laboratory environment. For reference, a human hair measures approximately 50 µm and the smallest particles that can be identified with the human eye are approximately 40 µm long. These 12 particles are then divided into three different size ranges (E1, E2, and E) and four sub-ranges that exist within each range.

The first range, E1, includes particles with a size of 0.3 to 1.0 µm. The E2 includes particles of a size of 1.0 to 3.0 µm, and the E3 encompasses particles of a size of 3.0 to 10.0 µm. The finer particles will have no problem getting through a fiberglass filter, and the larger ones will be filtered less effectively than with a pleated filter. This means that 81.5% of the dust particles introduced into the MERV filter were successfully filtered from the air.

Meanwhile, air filters with a MERV 14 rating or higher are designed for commercial HVAC systems that can withstand the coarser filter material. Based on the characteristics mentioned above, MERV 8 is considered superior compared to air filters with lower MERV ratings. Filters with a MERV rating of 8 to 13 are usually high-end filters for domestic use or high-quality commercial filters. The rating gives you an idea of its performance so you can make an informed decision when buying an air filter; using an air filter with a MERV rating that is too high is just as bad as using one that is too low.

These filters will capture a large part of the particulates suspended in the air and improve indoor air quality without significantly increasing energy costs. In 1987, the American Society of Heating, Refrigerating, and Air Conditioning Engineers designed the MERV rating scale to provide a more accurate picture of an air filter's capabilities; MERV ratings range from 1 to 20, with 1 being the lowest level of filtration and 20 being the highest. Both MERV 8 air filters and MERV 11 air filters are suitable for residential use; however, if you're concerned about inhaling fine air particles then you should opt for a higher rated filter such as MERV 11 for better protection.