Some companies use their own rating system instead of the MERV rating system. Home Depot uses FPR (FILTER PERFORMANCE RATING) and 3M uses MPR (MICRO-PARTICLE PERFORMANCE).
2. MERV 8 is comparable to MPR 600 and FPR 5 and is a good level to begin to protect air quality in your home. MERV 11 is Comparable MPR 1000-1200 FPR 7. and MERV 13 is Comparable MPR 1500-1900 FPR 10 and are used in superior commercial buildings and in homes with allergy sufferer.