The Minimum Efficiency Reporting Value (MERV) rating measures a filter’s effectiveness at capturing particles ranging from 0.3 to 10 microns in size. Developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), this rating system helps you compare the performance of different filters.
The MERV scale ranges from 1 to 20, with higher numbers indicating a greater ability to trap particles. A higher MERV rating means the filter is better at capturing smaller and more challenging particles, improving air quality more effectively. For detailed information about MERV ratings, visit ASHRAE’s official website.
| MERV Rating | Average Particle Size Efficiency in Microns |
|---|---|
| 1-4 | 3.0 – 10.0 less than 20% |
| 5 | 3.0-10.0 greater than or equal to 20% |
| 6 | 3.0-10.0 greater than or equal to 35% |
| 7 | 3.0-10.0 greater than or equal to 50% |
| 8 | 1.0-3.0 greater than or equal to 20% 3.0-10.0 greater than or equal to 70% |
| 9 | 1.0-3.0 greater than or equal to 35% 3.0-10.0 greater than or equal to 75% |
| 10 | 1.0-3.0 greater than or equal to 50% 3.0-10.0 greater than or equal to 80% |
| 11 | 0.30-1.0 greater than or equal to 20% 1.0-3.0 greater than or equal to 65% 3.0-10.0 greater than or equal to 85% |
| 12 | 0.30-1.0 greater than or equal to 35% 1.0-3.0 greater than or equal to 80% 3.0-10.0 greater than or equal to 90% |
| 13 | 0.30-1.0 greater than or equal to 50% 1.0-3.0 greater than or equal to 85% 3.0-10.0 greater than or equal to 90% |
| 14 | 0.30-1.0 greater than or equal to 75% 1.0-3.0 greater than or equal to 90% 3.0-10.0 greater than or equal to 95% |
| 15 | 0.30-1.0 greater than or equal to 85% 1.0-3.0 greater than or equal to 90% 3.0-10.0 greater than or equal to 95% |
| 16 | 0.30-1.0 greater than or equal to 95% 1.0-3.0 greater than or equal to 95% 3.0-10.0 greater than or equal to 95% |
| High efficiency Particulate Air filter HEPA* | 99.97% of particles in the 0.3-micron range Particles that are larger or smaller than 0.3 microns are captured with a greater than 99.97% efficiency |
A HEPA filter, which stands for High Efficiency Particulate Air filter, is a type of pleated mechanical air filter defined by the U.S. Department of Energy. It is designed to remove at least 99.97% of airborne particles as small as 0.3 microns in diameter. This size represents the “most penetrating particle size” (MPPS), meaning it is the most challenging for the filter to capture. HEPA filters are actually even more effective at trapping particles both larger and smaller than 0.3 microns.
To ensure that your air filter continues to work effectively, it’s important to perform regular maintenance and replace the filter according to the manufacturer’s recommendations.
