HEPA stands for High Efficiency Particulate Air
Generally all purifiers use one of the two types of filters – Composite and HEPA composite. The ideal preference for anybody should be a HEPA filter.
HEPA filters are considered far much better at separating pollutants from air. A true HEPA filter removes 99.97% of harmful particles that have a size less than 0.03 microns (To give you a better idea of the size of a micron, consider that we cannot visually see anything less than 10 microns. Bacteria can be anywhere from 0.3 to 60 microns, and 1 inch equals 25,400 microns).
HEPA filters are the only filters which meet specific EPA standards for efficiency and safety.
To put it simply, HEPA filters trap air contaminants in a complex web of fibers as shown in the image above.
Are all HEPA filters the same?
Contrary to popular belief, not all HEPA filters are the same. There are significant differences in composition and utilisation. Each company usually develops its own technology so as to get an edge in market. To get a HEPA filter tag, Institute of Environmental Sciences and Technology, USA dictates that a HEPA filter must trap 99.97% of particulates of 0.3 microns or larger. This does not mean that the filter cannot trap particles smaller than 0.3 microns, because many HEPA filters can; it is simply the threshold that must be reached in order to carry the HEPA name.