MERV is the acronym for “minimum efficiency reporting value” and is used to rate the efficiency of HVAC air filters. Generally speaking, the higher the rating the more efficient the filter. All air filters have holes in them to allow for the passage of air. Naturally this also allows particles to pass through, but the smaller the holes the fewer particles that are allowed to pass through with the air flow. MERV ratings rank in opposition to size, meaning that smaller filter holes get higher MERV rating numbers. Cool Zone recommends that their customers look for air cleaners rated at 10 or higher.