How do air filters work to improve indoor air quality?

Air filters work to improve air quality by using a blower or fan to pull air through the filter and then capturing particulate matter such as dust, mold spores, mildew, pollen, dust mite parts, cat and dog dander, and many more contaminants and pollutants. The filter material has tiny, microscopic opening that will let the cleaned air through while preventing the bigger contaminants and pollutants from getting through. Additionally, many filters have a natural electrostatic charge that is created by the moving airflow. The electrostatic charge attracts and traps many of the contaminants and pollutants in the air.

It should be noted that to get really good quality indoor air you should use a MERV 11 or MERV 13. These filters have been tested by "The American Society of Heating, Refrigerating, and Air-Conditioning Engineers".  Tests on filters that get a designation of MERV 11 and MERV 13 have scientifically shown that these air filters are capable of capturing as much as 80% to 90% of microscopic particles in the range of 1.0-3.0 micron in size. 3 microns is equivalent to .00011811 Inches, To further illustrate how small 3 microns is, the dot inside the parenthesis ( . ) is 615 microns.

Another factor for improved indoor air quality is the depth of the filter. A five inch deep filter has more area than a one inch filter, therefore the five inch filter has more holding capacity and can trap more particles, providing you with cleaner, healthier air in your home.