Ratings are used to rate the ability of an air conditioning filter to remove dust from the air as it passes through the filter. is a standard used to measure the overall efficiency of a filter. Higher ratings mean fewer dust particles and other airborne contaminants pass through the filter.
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 filter and after it leaves the filter. The two particle counts are compared to calculate the Particle Size Efficiency of the tested filter. Once this is determined, a Parameters chart is used to determine the rating.
Ratings range from 1 – 16 and measurements are in microns. Some of the common particles related to ratings are pet dander, insecticide dust, smog, dust, viruses, wood, tobacco smoke, spores, bacteria and pollen.
Some of the most common filters found in residential use only have a rating of 1 to 4.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.