MERV Rating, or Minimum Efficiency Reporting Value, is an industry-standard for measuring the efficiency of air filters. The lowest possible MERV rating is 1, while the highest efficiency rating is 20. Lower MERV rated filters will trap larger particulate in the air while filters with higher ratings will trap smaller particulate. Generally speaking, MERV 8 filters are recommended for most residential use as are MERV 11. Again, the higher the MERV rating the greater the filter’s ability to trap finer airborne particulate.