HEPA filter
A defined standard rather than a marketing word: at least 99.97 per cent of particles 0.3 microns and larger. Below that, the claim means nothing in particular.
In detail
HEPA stands for High Efficiency Particulate Air, and unlike most terms on a cleaning product it has a number attached. The federal conservation guidance states it plainly: a HEPA filter must remove at least 99.97 per cent of particulates 0.3 microns or larger in size, and any vacuum purchased should remove particles to at least 0.3 microns. ULPA — Ultra Low Penetration Air — reaches 0.12 microns and is described as appropriate for specialised projects. The figure matters because a vacuum's exhaust is the other half of its job: a machine that lifts fine particulate from a floor and returns it to the air has moved the problem rather than solved it, and the particles small enough to stay airborne travel furthest and settle slowest. The same guidance names when filtration stops being a preference: HEPA is especially essential if items may contain mould, pesticide dusts, lead, arsenic, asbestos, insect eggs, SOOT or other contaminants. Soot appears in that list because wood soot is an inhalation exposure rather than merely a mark. In a dry vacuum the HEPA element sits last in a chain — bag first for the large material, then additional filters, then HEPA for the smallest.
What works
HEPA filter is effective against House dust mites Supported
It removes surface dust and the skin scale that feeds them. It does not reach a population living through the depth of a mattress.
HEPA filter is effective against Dust Supported
The specification is numeric and worth knowing: at least 99.97% of particles 0.3 microns or larger.
Why
- HEPA filter is explained by Clogging the thing that does the work
The same failure in different equipment: capture depends on open structure, and a loaded filter looks much like a clean one.
Sources for this page
Sources
Conserve O Gram 1/6: Choosing a Museum Vacuum Cleaner
National Park Service, US Department of the Interior, 2003 · Government or regulator
Relied on for: That a HEPA filter must remove at least 99.97 per cent of particulates 0.3 microns or larger, that ULPA reaches 0.12 microns, that HEPA is especially essential where items may contain mould, pesticide dusts, lead, arsenic, asbestos, insect eggs or soot, and that dry vacuums filter in stages. (states this directly)
Wood Soot — Dangers to the Chimney sweep and stove installer!
Sweep Safe, United Kingdom · Trade or professional body
Relied on for: That wood soot is an inhalation exposure requiring respiratory protection rather than merely a mark. (states this directly)