ARSD 44:70:10:22. Filtration

A ventilation system using a recirculated central air system must be equipped with a filter bed. The filter bed must be located upstream of the conditioning equipment and must have a minimum efficiency of MERV 7. These filter efficiencies must be warranted by the manufacturer and must be based on the ASHRAE 52.2, 2012 edition, American Society of Heating, Refrigeration, and Air Conditioning Engineers.