The acronym HEPA stands for High Efficiency Particulate Arrestance (you may see others using variants for the letter “A” like arresting, arrestor, or even simply air, but they all convert the same basic meaning ‘to capture’) A ‘true’ HEPA is also known as an ABSOLUTE filter because of its efficiency. For a filter to be called a True Hepa it must retain and filter out all particles from the air that passes through it down to 0.3 microns in size at an efficiency rating of 99.97%. The efficiency of a true Hepa does not decrease during its life; it actually increases. For a filter to be labeled ‘True Hepa’, it must be certified 99.97% efficient in capturing 0.3 microns respirable-size-particles (RSP) according to the U,S. Millitary standard MIL-STD-282 commonly known as the D.O.P.test. True Hepa filteration is recognized as one of the must efficient air filteration methods known and proven to remove airborne particles down to 0.3 microns and are used for the purpose of absolute filtr