MERV and 3M Performance Rating
MERV stands for Minimum Efficiency Reporting Value and is a number from 1 to 12, produced from a test designed by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). The MERV rating is intended to help people compare filters and a higher MERV rating indicates better filter performance. The 3M Filtrete Ultra Allergen filter is rated MERV 11. 3M also produces ratings which focuses on a filter's performance at capturing the smallest airborne particles measured in the ASHRAE test. 3M uses particle data between 0.3 and 1 micron in size to calculate a Microparticle Performance Rating or MPR. The 3M Filtrete Ultra Allergen filter receives an MPR of 1250.