The Norse pure MERV 12 anti-allergen folded air filter is the nonesuch to reduce mobile contaminants in your home or business. With each pass through your MERV 12 anti-allergen folded air filter, the air in your environment. This static air filter and captures mobile dust, pollen, mold spores, pet dander, smog, dust small indefinite quantity debris, and baking flour. The MERV 12 anti-allergen folded air filter is of artificial material that will not support the growth of mold and bacteria. Along with the reduction of dust on surfaces, this MERV 12 anti-allergen folded air filter is a elation efficiency that will attract and capture the minute, allergy-aggravating micro-particles that can cause your family discomfort. The Norse pure anti-allergen folded air filter a Minimum Efficiency Reporting Value -LRB- MERV -RRB- of 12 which means that it will collect more than 90 % of 3.0-10.0 microns of contaminants, and up to 90 % of particles 1.0-3.0 microns. Particles in interior air are in microns, which are 1/1000 of a millimeter. A being hair is about 70 microns. The MERV 12 anti-allergen folded air filter is to a filter with a MPR rating of 1500-1900 and is a enthusiastic start to creating a able-bodied environment. Norse pure air filters an real size that is a fraction of an inch smaller than the specified size. With the 4 '' and 5 '' air filters there a wide variance between the specified size and real size. Almost ALL filters a dissimilar real size than the specified size printed on the filter so it is best if you measure your filter for the postulate size and compare it to our `` Actual Size. This why we ask you to measure your filter so you are n't surprised if the filter does n't fit ! . Our MERV 12 four or five inch air filter should be at least every 6 months depending on your environment. Changing your air filter at the recommended time will maintain a able-bodied environment as well as keeping your air conditioning and heating systems running efficiently.