How HEPA filters in aircraft help protect passengers from Covid-19

Fear among air passengers that the coronavirus could spread in flights has kept seats empty in many routes, since domestic airlines restarted operations from May 25.

But, can the virus spread board an airplane ? Not really, say airlines, aircraft manufacturers — both Airbus and Boeing — and the International Air Transport Association (IATA). Modern aircraft protects passengers from viruses — thanks to HEPA (High Efficiency Particulate Air) filters, they say.

HEPA aircraft filtration systems offer a level of performance similar to those used to keep air clean in hospital surgical rooms. The filter removes 99.99 per cent of dust particles and airborne contaminants such as viruses and bacteria. A constant downward wash of air at 1 metre/sec reduces the risk of cross-contamination. All the air in the cabin is fully filtered and renewed every 2-3 minutes, AirAsia said in its social media page.

How HEPA filters work

Air from the cabin is cleaned in the AC unit and in its HEPA filters; this clean recycled air is then mixed with fresh air from outside in the mixing unit and the pure, clean air is then passed into the cabin and circulates downwards to repeat the process, said IATA.

HEPA filters are effective at trapping microscopic particles as small as bacteria and viruses, IATA said in a paper, Cabin air quality – Risk of communicable diseases transmission, published in 2018. The paper was assembled from information provided by Airbus, Boeing and Pall Corporation.

The cabin air system is designed to operate most efficiently by delivering approximately 50 per cent outside air and 50 per cent filtered, recirculated air. This normally provides 15-20 cubic feet of total air supply per minute per person in economy class. The total air supply is essentially sterile and particle-free, said IATA.

According to Airbus, HEPA filters remove 99.99 per cent of particulate and organic matter, including microbes, from the air which is recirculated.

Boeing says most airplanes offer extremely clean air thanks to HEPA filters, which catch particulates down to the size of viruses. However, HEPA filters are not equipped to filter gaseous molecules. By increasing the humidity and adding new filtration technologies, studies show that the number of passengers experiencing the symptoms associated with dryness can be reduced, says a backgrounder on Boeing 787 Dreamliner.

Despite all the assurances, it will take time for people to overcome fear. A lot of awareness need to be created assuring safety of passengers on board, said an aviation expert.