MERV rating and what is MERV?

In the simplest terms, MERV measures how much matter passes through an air filter. MERV stands for Minimum Efficiency Reporting Value. MERV ratings are on a scale of one to 20 depending on the minimum size of the particles a filter can be expected to capture:

• A filter with a MERV rating of one to four captures particles greater than 10 micrometers. This includes bugs, dust mites, and household debris. Most window air conditioners fall within this range.
• A filter with a MERV rating of five to eight captures particles greater than three micrometers. This includes mold, pet dander, and aerosol sprays. This is the baseline for permanently installed residential air conditioners.
• A filter with a MERV rating of nine to 12 captures particles greater than one micrometer. This includes most dust and common pollutants. Hospital laboratories and superior residential air conditioners fall within this range.
• A filter with a MERV rating of 13 to 16 captures particles greater than 0.3 micrometers. This includes bacteria, droplets from sneezing, smoke, and most other sources of pollution. This level of filtration is used in patient and surgery areas of hospitals.
• A filter with a MERV rating of 17 to 20 captures virtually all particles. This includes viruses and the finest particles of smoke, dust, and other debris. This level of filtration is typically only used in clean rooms for the manufacture of electronics or scientific experiments.