What are HEPA filters and how effective are they?

14 Oct 2020 by Seher Asaf
HEPA Filter Diagram a321neo

One concern for passengers as they consider returning to the skies is how clean is the air on planes?

As far as the airlines are concerned, the answer is ‘Very’

This is because of the use of High-Efficiency Particulate Air (HEPA) filters, which are also found in hospitals around the world. 

Oman Air HEPA-Filters

The air on most modern commercial aircraft is a mix of recirculated air and outside air.

In fact, according to the The Centers for Disease Control and Prevention, all commercial jet aircraft built after the late 1980s recirculate between 10 to 50 per cent of the air in the cabin, mixed with outside air.


In most newer-model airplanes, the recycled air passes through HEPA filters, which capture 99.9 per cent of particles (bacteria, fungi, and larger viruses or virus clumps) measuring 0.1–0.3 micrometers in diameter. The virus that causes Covid-19 is approximately 0.125 micrometers (125 nanometers) in diameter, according to a study published in the Nature Public Health Emergency Collection. This fits into the size range captured by HEPA filters.

Since the start of the pandemic, almost every major airline in the world has been emphasising the role of these filters in their fleets.

For example, American Airlines says in its Airbus A320 and Boeing 737 families of aircraft, air is filtered through two HEPA filters located near the forward cargo compartment.

On its largest aircraft, the B777 family, there are eight HEPA filters – four near the forward cargo compartment and two over each aisle near the middle of the aircraft cabin. Filters are changed regularly to ensure the uninterrupted flow of clean, fresh air into the cabin.

Other measures

HEPA filters are only one piece of the puzzle when it comes to preventing the spread of a virus. 

Covid-19 is primarily transmitted through person-to-person contact and through contact with droplets released through coughing from an infected person.

Other safety measures include requiring face masks, disinfecting aircraft and offering pared down services to reduce contact between passengers and crew. You can read more about those safety measures in the next issue of Business Traveller magazine, out in November.

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