Detailed Working Description of HEPA Filters
HEPA stands for “high efficiency particulate air”. HEPA filters can trap a large amount of very small particles that other vacuum cleaners would simply recirculate back into the air of your home. HEPA filters are composed of a mat of randomly arranged fibres. Key metrics affecting function are fibre density and diameter, and filter thickness. HEPA filters are designed to trap much smaller pollutants and particles by any one of the following mechanisms:
- Interception, in which particles following a line of flow in the air stream come within one radius of a fibre and adhere to it.
- Impaction, in which 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.
- Diffusion, in which there is collision with gas molecules by the smallest particles which are thereby impeded and delayed in their path through the filter. Diffusion, is able to filter the smallest of particles.
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