If there’s one thing we’ve heard wheeled out by practically every airline as they look to resume flying, it’s the concept of HEPA filters. In a bid to encourage passengers back to the skies, airlines are shouting loud about the quality of the air onboard the plane, and their ‘hospital-grade’ filtration systems. But what are HEPA filters, and can they really make flying safe again?
What is a HEPA filter?
Standing for High Efficiency Particulate Air filter, the HEPA technology onboard aircraft is used in other products around the world, including vacuum cleaners. They work through the use of close-knit fibers that trap impurities from the air, removing them from circulation.
It’s not just dust and dirt that the filters remove. They are so good at removing particles, they can extract bacteria, moisture and, crucially, viruses. Since the 1980s, most commercial aircraft have had these types of filters fitted to maintain the cleanliness of the cabin air.
Do HEPA filters protect from coronavirus?
According to the Centers for Disease Control and Prevention (CDC), HEPA filters capture 99.9% of particulate matter from the air, including fungi, bacteria and viruses, from 0.1 – 0.3 micrometers in diameter. Studies of the coronavirus linked to COVID-19 have shown that the viral particles, or virions, range in size from 0.06 to 1.4 micrometers, with an average size of 1.
Coronavirus is typically sized 0.1 micron, so HEPA filters on aircraft will effectively remove 99.97% of the C-19 virus. pic.twitter.com/sKp45nkusg
— Mark Handford✈️ 🎮 (@Mark_Handford) May 30, 2020
While that doesn’t sound great, it’s important to remember that the virus is not airborne. Although the smallest individual virions could indeed slip through a HEPA filter, they would never end up there unless they were contained within a respiratory droplet.
Respiratory droplets, produced when people, cough, sneeze, breath and even talk, range in size from 5 micrometers up to as big as 10. They are still invisible to the naked eye, but in terms of HEPA filtration, they’re huge.
The downside of the coronavirus not being airborne is that, by piggybacking on respiratory droplets, it has the opportunity to land on flat surfaces. In a home environment, a HEPA air purifier would be unable to eliminate the droplets at a sufficient rate to stop them from settling on surfaces. For this reason, home-based air purifiers, even those with HEPA filters, would be unlikely to protect you from COVID-19.
However, on an airplane, it’s a different story.
Why HEPA filters work on planes
The reason HEPA filters do provide protection on a plane but wouldn’t at home is because of the rapid circulation of air in the cabin. On a typical narrowbody (A320, Boeing 737), the air is completely renewed every two to three minutes, or 20 – 30 times every hour. The cabin air is a mix of fresh air (around 60 – 70%) and recirculated air.
Cabin air renewed every 2 to 3 minutes, #HEPA filters and top to bottom air circulation ensure aircraft cabins are a safe environment.
Be in the know: watch how cabin air is kept clean from bacteria and viruses as it flows in and out of aircraft. #KeepTrustInAirTravel #COVID19 pic.twitter.com/3wvGQRTxU0
— Airbus (@Airbus) June 2, 2020
Even more crucially, the air is not circulated around the aircraft in a way that would allow the virus to pass by other passengers. Air is sucked out of the cabin using vents in the floors, passed through HEPA filters, mixed with fresh air from the outside and injected back in through air outlets and individual vents.
It’s a common misconception that air on board is recirculated. All our aircraft are equipped with an industry-leading air circulation system containing a HEPA filter. Our aircraft also introduce fresh air into the cabin every two to three minutes. pic.twitter.com/l7OLb4QtnJ
— WestJet (@WestJet) June 11, 2020
This vertical movement of air forms a protective barrier between rows, making it highly unlikely that the virus could pass between passengers seated in front or behind each other.
Primero debe usarse mascarilla (y bien, no como el que gritaba en el video)
Y segundo el flujo de aire hace que el virus expulsado baje a la zona del suelo en pocos segundos donde permanece más tiempo hasta ser eliminado.
Tiempo total: de 2 a 3 minutos
Foto ilustrativa: pic.twitter.com/jHS6ZhDzfE
— SCIENCE UNPOPULAR OPINION (@SCIUNPOPOPINION) May 11, 2020
This, coupled with the enhanced cleaning measures being undertaken by airlines as well as the ever-expanding requirement for face coverings, will ensure that passengers are as safe as possible when they are ready to return to flying.
Do you feel confident in the capabilities of HEPA filtering? Let us know in the comments.