ASHRAE Standard 62.2 requires that particulate air filtration of no less than MERV 6 efficiency is installed in any HVAC system having more than 10 ft of ductwork. The particulate filter must be installed such that all of the air circulated through the duct system is efficiently filtered prior to passing through the thermal conditioning portion of the system. In addition, the standard requires that the filter be located and installed for easy access and service by the owner or operator. Lastly, the standard requires that the filter cartridge be sized to operate at no greater than 0.1 inch water column when clean, or that the air handler be selected to handle greater pressure loss without undue restriction on airflow.

Many industrial and commercial systems have factory or OEM installed filter cartridges that comply with this minimum filtration requirement. These are normally 1-inch thick with a pleated media configuration to attain the proper efficiency and airflow performance.