Furnace Filters

Furnace Filters

MERV ratings are determined by adding particles of varying sizes (1-12) into a controlled testing environment. The particles are added upstream of the test filter and a laser particle counter samples the air before it enters the furnace filter and after it leaves the furnace filter. The two particle counts are compared to calculate the Particle Size Efficiency of the tested furnace filter. Once this is determined, a MERV Parameters chart is used to determine the MERV rating. MERV ratings range from 1 - 16 and measurements are in microns. Some of the common particles related to MERV ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.