People in the Air Filtration Industry can understand when you say a filter is 30%, 95%, or 99.97% efficient, but cannot understand as well if you say the filter has a MERV 7, MERV 14, or MERV 17 rating which would correspond to the aforementioned efficiency levels. AER Control Systems manufactures many different types of units that filter dust, mist, fume, and smoke. The AER Control Systems filters are set up so that the less efficient filter is first in the dirty airstream followed by a series of more efficient filters. The number and type of different efficient filters depends on how large and small the particles are in the airstream. See below some of the common filters that AER Control System uses with references to the old understanding of efficiency in percentage and the filter MERV rating.