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.Some of the most common furnace filters found in residential use only have a MERV rating of 1 to 4. Often times these furnace filters are not assigned a MERV rating. These are typically disposable panel type filters and do not do a good job of filtering the air because they will not stop particles smaller than 10 microns.
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Using efficient replacement air filters is important in helping to control household allergens. There are many types to choose from and it can be confusing. This article introduces the most common types of air conditioner filters and furnace filters.
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