MERV Rating
Minimum Efficiency Reporting Value, an HVAC industry filter rating from 1 to 20.
MERV is used for furnace and air-conditioning filters, not vacuum filters. A MERV 13 HVAC filter captures roughly the same particles as a true HEPA filter; MERV 17 to 20 is HEPA tier. Mentioned here because HVAC and vacuum filtration overlap in allergy-sensitive households.