When you think of a sieve you use whilst cooking, that’s how a HEPA filter works. A HEPA filter is usually rated at its efficiency at removing particles of 0.3 micrometre (micron), they can capture below this size but 0.3 is the most difficult size to capture. Below 0.3 microns the particles are affected by Brownian motion, this random motion gives the particle a greater effective diameter and so aids capture. Larger particles will tend to move in a straight line due to inertia and so become easier to capture.

 

HEPA filters provide high efficiency filtration, hence why HEPA stands for “High Efficiency Particulate Air”. 

Particles that HEPA filters can capture:

 

  • Dust and dust mites
  • Mould
  • Human hair
  • Bacteria
  • Tobacco smoke

 

You will find most modern vacuum cleaners contain HEPA filters, but they are also used in factories, warehouses, hospitals and many other places where health and safety measures are critical. 

HEPA filters work best on dry particles which is why they are not really suited for mass virus removal. Viruses are only viable in a fluid environment. HEPA filters will work to remove the virus but will have a limited life span as the media will become blocked prematurely.

 

HEPA filters go back to WW2, where they were used to protect the soldiers from gas attacks. 

 

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