A HEPA filter, which stands for High Efficiency Particulate Air filter, is a highly effective type of air filter designed to capture airborne particles. Officially defined by the U.S. Department of Energy, a true HEPA filter can remove at least 99.97% of particles as small as 0.3 microns in diameter. This size represents the “most penetrating particle size” (MPPS), meaning it is the hardest size for the filter to capture. However, HEPA filters actually trap particles both larger and smaller than 0.3 microns with even greater efficiency.
To ensure optimal performance, HEPA filters require regular cleaning and replacement according to the manufacturer’s guidelines.
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In addition to HEPA ratings, filters are also evaluated based on their Minimum Efficiency Reporting Value (MERV). This scale 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), the MERV rating helps compare the performance of different filters, with higher ratings indicating better particle capture capabilities.
For more information on MERV ratings, visit ASHRAE’s official website.
| MERV Rating | Average Particle Size Efficiency in Microns |
|---|---|
| 1-4 | 3.0 – 10.0 less then 20% |
| 6 | 3.0 – 10.0 49.9% |
| 8 | 3.0 – 10.0 84.9% |
| 10 | 1.0 – 3.0 50% – 64.9%, 3.0 – 10.0 85% or greater |
| 12 | 1.0 – 3.0 80% – 89.9%, 3.0 – 10.0 90% or greater |
| 14 | 0.3 – 1.0 75% – 84%, 1.0 – 3.0 90% or greater |
| 16 | 0.3 – 1.0 75% or greater |