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Is air travel whilst wearing masks safer than we think? US Government study says it is

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In the last few weeks, a number of studies have been published that attempt to accurately model how easily SARSCoV2 viral particles spread inside aircraft cabins.

Historically, aircraft have had somewhat of a bad reputation for viral transmission. Intuitively, stuffing a narrow tube with passengers shoulder-to-shoulder seems like it would be a hotspot for contagion.

How safe is flying with a mask

The average passenger is unlikely to know that on modern aircraft, the cabin is filled with completely fresh air every 2-3 minutes, or that all recirculated air must pass through a High Efficiency Particulate Air (HEPA) filter that is capable of removing most bacteria and viruses from the air.

I have had numerous conversations with friends and family who were surprised to find this out!

How do we establish aircraft transmission?

In the past months, several studies have been published on the transmission of coronavirus during air travel.

Three studies were published last month looking at three separate flights that resulted in ‘probable’ in flight transmission:

  • A Vietnam Airlines flight from London to Hanoi on 1st March resulted in a cluster of 16 cases
  • A flight from Boston to Hong Kong on 9th March resulted in a cluster of four cases (two crew, two passengers)
  • A flight from Athens to Tel Aviv in February or early March resulted in a cluster of five cases

All studies rely on retracing the likely path of transmission from contagious ‘index’ patients to the subsequently infected by calculating incubation periods, proximity to index patients and in some cases genomic sequencing to verify if the virus in index and infected cases are related.

It is worth noting that the studies are based on cases when masks were not mandatory during flight.

On the other hand, IATA, the International Air Transport Association, published a study recently that identified only 44 cases of potential flight-related transmission:

“The risk of a passenger contracting Covid-19 while on board appears very low, with only 44 identified potential cases of flight-related transmission among 1.2 billion travellers, that’s one case for every 27 million travellers.

“We recognise that this may be an underestimate, but even if 90% of the cases were unreported, it would be one case for every 2.7 million travellers. We think these figures are extremely reassuring.”

How safe is flying with a mask

Computers good, real life better

Up until now, questions of flight-related Covid-19 exposure have been based on case studies or computational fluid dynamics, with Airbus and Boeing both studying how aerosols behave in a cabin environment.

There is only so far that computational models can go when modelling the dispersion of aerosols and droplets in aircraft cabins. Questions have been raised about “simplistic” models used by aircraft manufacturers:

“It is difficult to determine the potential exposure risk using available computational fluid dynamics models or contact tracing methods, due to the lack of experimental validation of aerosol transport in the aircraft environment and the lack of detailed tracking of human interactions in aircraft.” (United Airlines study)

We now have something better. This week, the US Department of Defense and United Airlines published a landmark study on the safety of commercial air travel based on real-life scenarios in controlled environments.

How safe is flying with a mask

The study used two United aircraft, a Boeing 777 and a Boeing 767, across 38 hours of flight time and 45 hours of ground-based testing.

Over 300 aerosol release tests were performed, with each releasing over 180 million fluorescent aerosol tracers. The aerosol tracers were ‘exhaled’ by a mannequin called Ruth to best simulate the release of the virus by breathing and coughing, both with a mask on and off.

How safe is flying with a mask

Each surrounding seat in the cabin section contained a bio-defense sensor capable of detecting the aerosols in the cabin air, representing the other passengers in the cabin. Sensors were also placed in galleys and the jetbridge during ground testing.

In addition, thermal blankets were used to simulate the body heat of passengers and subsequent heat emission and potential convection currents generated.

United coronavirus transmission study cabin

Results show extremely low rates of transmission

Once all the numbers had been crunched, the study found that only 0.003% of particles actually made their way into another passenger’s breathing zone when seated and wearing masks. To put it another way, this is only one in every 33,000+ particles.

In addition, around 99.99% of all particles were filtered out of the cabin air within six minutes due to air circulation, ventilation and filtration.

Put another way, the test:

“indicates an extremely unlikely aerosol exposure risk for a 12 hour flight when using a 4,000 virion / hour shedding rate and 1,000 virion infectious dose.”

With evidence mounting that aircraft themselves are very safe provided masks are worn, it now seems that other areas of the passenger experience – such as at the airport itself or public transport – are more likely to result in transmission of the SARS-CoV-2 virus.

You can read the full results here.

Comments (83)

  • Iain miller says:

    Would have been interesting to know the results had the did the same without the other “passengers” wearing masks.

    I suspect the results might not have been correct in the current political climate

  • lcylocal says:

    Worth also being aware of study’s highlighted in this week’s SAGE papers that showed the proper use of disposable medical masks cuts the inhalation of particles by between 40-50% (this was not the case though for reusable fabrics face coverings which only provide protection to others).

    My experience of flying is that compliance is good apart from people who linger over food and drink. For short haul wearing one for the best part of 5 hours from leaving the lounge to leaving the airport on arrival didn’t seem particularly uncomfortable or problematic at all for me (and I have asthma so I’m probably exempt in theory).

    • Polly says:

      That’s useful to know. I am asthmatic also, most l wear one now is an hour probably. But, not flying atm due to OH, so probably won’t be in a position to wear one even for SH, sadly.

  • Andrew says:

    With all this mask wearing and social distancing none of us are going to catch colds this winter! Beechams night go out of business.

    • Nadeshka says:

      Unless you have kids at school or nursery. Ours started 2 months ago and I think we’re on cold number 4 already.
      But yes during lockdown we had none at all!

    • ChrisBCN says:

      There’s some truth to that… The flu season in Australia didn’t happen this year, probably (though I don’t think proven conclusively) due to mask wearing.

      • Louie says:

        I doubt that mask wearing had anything to do with it. Since this all started I doubt if I’ve seen more than a dozen people in total wearing masks (I’ve not been in Melbourne obviously). Much more likely much more washing of hands and social distancing / lockdowns and kids being out of school. According to this article – https://www1.racgp.org.au/newsgp/clinical/flu-boosters-unnecessary-as-influenza-all-but-vani July 2020 had 192 cases compared with 70,071 case in the same month the previous year, a fall of 99.7% (according to me, 99.997% according to them). Amazing.

    • Jody says:

      I thought the same, however my husband is on day 4 of an absolute stinker of a cold!

      He works from home and always masks up outside the home, so not really sure how that happened!!

    • Charlieface says:

      So far two sets of colds, and a nasty 24hr stomach bug, in our house of 3 little ones since March

  • Nick says:

    Curious to know why the DOD funded this study into virus distribution rather than (say) DOT… Perhaps I’m too cynical.

    As for masks, they really should simulate what happens if people wear it over their chin, or perhaps mouth but not nose. As that’s how most people did on the (admittedly few) flights I’ve been on.

    • ankomonkey says:

      Absolutely. The number of people I’ve seen on or off planes wearing masks over their mouth but not their nose beggars belief.

      • Lady London says:

        And thr ones thar simply wont be stop talking non-stop (usually utter trivia bur continuous?) even when they’ve got a mask on which must increase the risk if escape of the vius from bwhind theur mask 100x

    • Dubious says:

      Maybe the DOD funded it because they were interested to know for the transportation of their military personnel?
      or maybe they recognise there is an element of defense in health and pandemics.

  • Scott says:

    As others say, the risk of Covid19 transmission is a complex mix of people interacting from arrival at airport to departure at the other end, plus any virus particles already on clothing, aircraft, consumables aboard aircraft etc. People (including airport staff, aircraft crew, passengers) can’t reliably wear masks 100% of the time. The risk presumably increases if there are multiple asymptomatic people all shedding virus. Even with pre/post flight tests there is a high false negative rate (relatively speaking). It’s a combination of protective measures that are needed, and I’m afraid until I’m able to actively protect myself from becoming infected or sick (as opposed to relying on others wearing masks to avoid transmitting infection to me) I’ll be reluctant to travel in public transport (air or otherwise).

    I suspect we will need a combination of widespread vaccination (to reduce prevalence and minimise time window for asymptomatic transmission), face masks, social distancing and who knows what else – to get safety that allows mass travel to return.

  • Harry T says:

    The real issue is when Ryanair serve groups of people continuous drinks, and said people shout at each other for the entire flight.

    EasyJet, by comparison, were excellent. They gently but firmly reminded passengers to wear their masks over their nose and mouth, including directly addressing offending passengers in a professional manner.

    I am constantly amazed by how people cannot tolerate wearing a disposable surgical face mask or thin cotton mask over their nose and mouth for a few hours. Healthcare professionals do this all the time.

    • meta says:

      BA is the same. They even encourage customers to take more drinks and food so they don’t have to wear a mask! On my recent flight CSM told me she doesn’t believe in mask wearing, so she will not say anything to the customers and will serve them more drinks. One guy kept ordering a glass of water from the moment the seatbelt sign went off till the end. The crew continued bringing him water even when the seatbelt sign was back on for landing. Needless to say he had a mask under a chin, I guess just for decorative purposes.

      I am also amazed. People overthink this. Just put the mask on and don’t think about it. After 5-10 minutes you won’t even realise it’s there. It’s similar to wearing glasses.

      • Harry T says:

        Couldn’t agree more. The thing about mask wearing is that it gets easier and more comfortable the more you do it.

        That’s shameful behaviour from BA cabin crew.

        The thing about masks is you wear them for the benefit of other people, which is why it’s so disappointing when fellow travellers don’t wear them properly.

      • Polly says:

        Photo of that packed flight from Belfast hardly a mask in sight, and every seat full… says it all. Crew say they can’t force masks. Well, US crew do.

        • meta says:

          Easyjet crew do. As Harry mentioned it, they have such a brilliant way of enforcing it. I took only one flight in August with them, but no one dared not to put the mask below the nose.

        • Bluekjp says:

          That picture was early lockdown. BA are very strict in the BHD route and all others.
          On my two Finnair flights in August they handed out to every passenger a leaflet explaining that the cabin air is akin to a hospital operating theatre with a diagram of air movement. I carry mine around to educate people who are always very pleasantly surprised. The same information was was also on ba.com very very early during lockdown.

          • meta says:

            No they are not! BA is the worst. The above experience is from my recent flight in early October. The problem is passengers carrying them, but clearly do not want to use them. There are loads of pictures and reports on a daily basis on Twitter about BA crew clearly not bothered about enforcing and passengers blatantly disregarding rules, even bragging about it. BA’s Twitter team response is that they are not going to enforce it or even ask people.

    • Chrisasaurus says:

      They can tolerate it just fine but in a world that has got all fast paced and competitive and scary to them they’re struggling for a sense of control and their hissy fit is their chance to claim a sense of mastery over their lives

  • Nick_C says:

    Well I for one am totally reassured by these reports from aircraft manufacturers and airlines.

    It’s reminiscent of the excellent scientific research that the Tobacco Industry used to produce showing that smoking is not detrimental to health and can even be beneficial.

    Independent research is for wimps.

  • BJ says:

    For the benefit and education of those who remain in denial see here: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext

    When extrapolating small reduction in person-to-person transmission through increasingly greater scales the benefits of distancing and masks become huge. Failure to act on this by individuals through governments in the spring was sad and frustrating; continuing failures six months down the road in a bloody tragedy.

    • Polly says:

      They did not want mask supplies depleted at that time, methinks, as there weren’t even enough for care homes, hospitals, volunteers etc..now of course they are everywhere, supermarkets etc. So hey ho, now it’s wear a mask everyone. And it doesn’t take long to get used to them…
      It’s one of the reasons you see people in Asia wearing them for years, even outside on the streets.
      Thanks for that BJ, it’s worth us all passing this along to everyone we know…the reduction is startling. Pure selfishness on people’s part not willing to play their very small role in prevention.

      Here in Elmbridge we went into Tier 2 last night. Trying v hard to find out where these infections are based. Not one member of staff in our Morrisons, Waitrose nor Tesco has even tested positive. It’s such a puzzle how it’s spreading. And l would have thought these people were at risk of viral load as supermarket staff.

      • Lady London says:

        Plus the price for the plain strinf disposable masks is down to the 10 cents or pence it should always has been as a max.

        I simply do not believe supermarkets and chemist shops – or their distributors – have not been profiteering.

        • BJ says:

          Obviously many have, you just need to search the prices of the same masks from different suppliers. I know that they too may have had to pay different prices but it is galling that some of our biggest retailers and most trusted brands are charging some of the highest prices. I know about free markets and all that but it is beyond me that in a public health emergency on the current scale that the government will not step in and take action.

      • Lady London says:

        To what extent do people think cases are being imported by arrivals into the UK?

        • BJ says:

          Now I think it is mostly community transmission within countries. The majority of travellers, like the majority in general, will now be exercising caution I believe. If anything, I suspect those travelling may be more cautious than those staying at home because nobody wants to get stuck in a foreign healthcare system if they can avoid it.

      • BJ says:

        Granted there was an issue with supply back in the spring which is no surprise and when rightly masks had to go where they were most needed. However, the benefits of wearing masks at the time were known and the government failed then, and continues to fail now, in deploying the power it has to secure a plentiful supply at a cost-effective price, and to compel people to wear them. Ofcourse, if many are going to continue to behave selfishly or idiotically then ultimately even the best efforts of any government will be undermined.

        • Polly says:

          Do you remember them burning a couple of million paper masks as they had expired! Seriously, who ever knew paper expired…l think they could have been useful in non hospital environments…was incensed when that news got out. Reason said that the stockpile had expired items…

          • Lady London says:

            Hum. I wonder how many of those masks that expired and were burnt actually ended up being sold somewhere.

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