What is a HEPA Filter?

High Efficiency Particulate Air Filters

A HEPA filter removes a minimum of 99.97% of contaminants at 0.3 microns in size. A micron is One one-thousandth of a millimeter. To help you better understand something that small consider the following example.
A human hair is about 60-75 microns in diameter. Particles under 35 microns in size can't be seen with the naked eye. Pollen is in the 10-100 micron size range with dust in the .5-5 micron range. Particles under the 5 micron size are the most troubling for asthmatics since that is the ideal size to penetrate deep into the lungs.

Different Types of Filters

There are many different manufacturers of HEPA filters. They work typically in the same way. Most all HEPA filter elements require frequent replacement. This is a key item to check before you purchase. There are many different manufacturers of HEPA filters. They work typically in the same way. Most all HEPA filter elements require frequent replacement. This is a key item to check before you purchase. A HEPA filter that costs a little less than the others, but requires more frequent filter replacement is not cheaper. Some available HEPA filters also contain ultraviolet light sources as well. Ultraviolet light can destroy mold spores, bacteria and some viruses including the influenza (flu) virus. Ultraviolet light does work and has been used in many hospitals for years to help kill bacteria in the air.What's a Micron?

A micron is a measure of length: "1 micron equals 1 millionth of a meter!". A particle that is 10 microns or less in size is not visible to the naked human eye. Examples of some common air contaminants and their size in microns: Human Hair ......................................... (70 - 100 microns) Human Sneeze ................................. (10 - 100 microns) Pet Dander .......................................... (0.5 - 100 microns) Pollen ................................................... (5 - 100 microns) Spores from Plants .............................. (6 - 100 microns) Mold...................................................... (2 - 20 microns) Smoke ................................................... (.01 - 1 micron) Dust Mite Debris ................................. (0.5 - 50 microns) Household Dust ................................. (.05 - 100 microns) Skin Flakes ........................................... (0.4 - 10 microns) Bacteria................................................. (0.35 - 10 microns)