Hepa Air Purifiers have become the gold standard for air purification. HEPA is almost like Frigidaire in that it has become a term representing the very best in its class, in this case for premium filters or air purification systems. What does HEPA mean anyway?

HEPA means A high efficiency particulate high-efficiency air filter. H.E.P.A.

Theoretically HEPA filters remove 99.7% of airborne particles of a size 0.3 micrometers in diameter.

Filters classified as HEPA filters are made up of a bed of random fibrous substance. The fibers are mostly composed of fiberglass and possess diameters between 0.5 and 2.0 micron. Key factors affecting function are fiber diameter, filter thickness, and face rate. The air space between HEPA filter fibres is much greater than 0.3 μm. The misguided theory is that a HEPA filter can allow particles smaller than the filter opening to pass is largely erroneous. Unlike membrane filters, where particles as wide as the largest opening or distance between fibers cannot pass in between them at all, HEPA filters are designed to target much smaller pollutants and particles. These particles are trapped through a combination of the following three mechanisms:

1. Interception, where particles following a line of flow in the air stream come within one radius of a fibre and adhere to it.
2. Impaction, where larger particles are unable to avoid fibres by following the curving contours of the air stream and are forced to embed in one of them directly; this effect increases with diminishing fibre separation and higher air flow velocity.
3. Diffusion, an enhancing mechanism is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 µm in diameter, which are thereby impeded and delayed in their path through the filter; this behaviour is similar to Brownian motion and raises the probability that a particle will be stopped by either of the two mechanisms above; it becomes dominant at lower air flow velocities.

Did you know the original HEPA filter was used to prevent the dissemination of airborne radioactive particles during the Manhattan Project? From that beginning the HEPA filter has become a common name and a generic term for highly efficient filters and HEPA Air Purifiers.