HEPA

 
HEPA is an acronym for “high efficiency particulate air”. Basically HEPA is a type of fiber that can trap a large amount of very small particles that other vacuum cleaners would simply re-circulate back into the air of your home. There are a couple of different categories of HEPA filters that can make understanding the abilities of your filter confusing.

As the smaller 2.5 micron particles in the air pass though this maze, they snag on one of the fiber and are held in place. Because these fibers are so dense the airflow through a sheet of HEPA filter is very constricted. Therefore the filter material is folded back and forth to present a very high surface area to the air stream and thus to allow sufficient airflow to make a HEPA air purifier affective. Typically HEPA filters will filter particulates of 0.03 micron size with an efficiency of 99.97%. However, the less expensive HEPA air purifiers often are subjected to a lot of blow-by. This means that air under power from the fan can move around the filter rather then though it.