When it comes to air filters, it's important to make sure you select the right one for your HVAC system. MERV stands for Minimum Efficiency Rating Value, a standardized system created by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE). This rating system ranges from 1 (lowest efficiency) to 20 (highest efficiency). E1, E2, and E3 particles are particle range sizes used in air filter tests to determine a MERV rating.
ASHRAE recommends MERV 13 and 14, but it's best to select a filter with the highest possible MERV rating for your specific HVAC system. To help you decide which filter works best, here is a comparison table of the differences between MERV 8 and MERV 11 filters. Most MERV 7 or higher air filters are effective at trapping dust, mold spores, tobacco smoke, pet dander and pollen. The higher the MERV rating, the more efficient the filter will be at trapping these particles in the air.
In contrast, a high MERV rating indicates that the filter does a good job of removing particles from the air. However, air filters with MERV ratings higher than 13 tend to restrict airflow because they have smaller pores to capture smaller particles. The table below shows the minimum threshold at which a filter must operate to obtain a specific MERV rating. Filters with higher MERV ratings should be changed more frequently (at least every three months) to avoid restricted airflow that can cause the system to operate inefficiently or even damage it.
The worst percentage of the six tests is selected as the official measure used to determine the MERV rating of a filter. With the Filter King filter selection tool, you can mark exactly the size, thickness and MERV rating you're looking for. Once you understand how the MERV rating table works, you can choose air filters with the MERV ratings that are right for you.