Are airplanes germ warehouses?

I hate traveling by plane for many reasons, mainly because of the cramped seats, the security theater one has to go through, and so on, though the convenience of getting to one’s destination so much more quickly usually outweighs the negative elements. I have a rule of thumb that says that if traveling by car to a destination takes six hours or less, or if there is no time constraint for even longer journeys, I prefer to drive.

Being afraid of picking up germs from other passengers has not been on the top of my list of concerns about air travel. I tend to ignore the risks of germs in normal life. But it is clear that fear of such germs has gripped many people. As a result of the recent fears about SARS and swine flu and bird flu epidemics, our university now installs anti-bacterial soap dispensers all over the place and I notice that the local supermarket provides such wipes and people use them to wipe down the handles of the shopping carts. I never use them.

To the extent that I thought about airplane germs, I thought that the greatest danger came from the air that was circulating in the confines of the cabin, due to having the vague idea that it was ‘recirculated’. But Robert T. Gonzalez explains that the air in the cabin is in fact likely to be cleaner than that in your typical office building, and that passengers have a very misguided idea of what recirculated air means.

In reality, however, the air you breath on a typical airplane flight is thoroughly clean. Fresh air from outside the plane is continuously drawn into the cabin via what are known as compressor stages in the jet’s engines. These stages compress the very cold and extremely thin air from outside the plane until its pressure matches that of the cabin. Pressurizing the air also heats it up, so it’s cooled back down before passing through High-Efficiency Particulate Air (HEPA) filters (which remove a minimum of 99.97% of any airborne particulates, bacteria and viruses) and combining with recirculated cabin air.

But there’s that word again. Recirculated.

Yes, the fresh air from outside the plane combines with some air that’s already been making the rounds in the cabin for a little while — but that circulating air started out as fresh external air itself, and it too has been cycling through HEPA filters. What’s more, recirculating cabin air is continuously released from the plane via outflow valves, so air inside the plane is constantly being replaced by the fresh air from outside. In fact, the average airplane’s cabin air is completely refreshed about 20 times per hour. By comparison, the air in your average office building (which is also typically HEPA-filtered) is refreshed just 12 times per hour. In other words, the air you breathe at cruising altitude is most likely significantly cleaner than just about any you’re liable to find on the ground.

This does not mean that air travel is more germ-free than everyday life. It is not. But the dangers come from other things like contact with surfaces that other people may have touched and Gonzalez describes the sources of the problem and what one can do about it.

I am not likely to follow his recommendations to use hand-sanitizers and the like, though. I tend to be the kind of person for whom taking a lot of steps to protect oneself from the environment is a lower priority than simply living one’s life with the minimal hassle and disruption.

Other people may arrive at a different conclusion.


  1. says

    I think people lump the terminals in with the air travel experience. And the terminals are a problem – you’re encountering pathogens from other travellers, that you may not have developed immunity to, yet. The big hubs are trading-centres for viruses on a grand scale – though I’d love to know if that’s better (herd immunity) for humanity, or worse. I read a book about the swine flu outbreak in WWI that killed so many people, and it seemed like one of the reasons it was so deadly was that not only was it a new strain of flu but it encountered population that had no resistance to flu at all like the Inuit.

    I have a friend who is a nursing student and is taking epidemiology right now, so as soon as she wakes up, I’ll skpe her and interrogate her! Thank you, internet!

  2. says

    I’ve found most who go on about the air (some pro- and some anti- “recirculated”) are the very same people who don’t cover their mouths and don’t wash their hands.

    Coughs and sneezes spread diseases is what I heard growing up, yet some think it isn’t necessary. They don’t want to catch a cold or flu from others, but don’t care if others catch it from them.

  3. says

    I’ve always been leery of hand sanitizer. Sure, they kill 99.7% of bacteria, but what are we going to do when the resistant 0.3% becomes dominant, the sanitizer becomes useless, and few people have resistance to it because people have worked so hard not to build up immunity? And does any of that stuff actually work on viruses? And how is it any better than simply washing your hands, which will never result in a resistant strain?

    On airplanes, I am far more concerned with the tray tables, magazines, windows, armrests and seat backs.

  4. daved says

    it seemed like one of the reasons it was so deadly was that not only was it a new strain of flu but it encountered population that had no resistance to flu at all like the Inuit.

    It was thoroughly deadly even to people who did have previous exposure to flu because, as you mention, it was a new strain. Ironically, it seemed to be even more deadly to young, healthy people, because it kicked their very healthy immune systems into overdrive.

    I saw a paper recently that suggested that hand sanitizers are not particularly useful, and cannot compare to a good washing with soap and water. Oh, and you don’t antibacterial soap; those damn things should be outlawed.

  5. Mano Singham says

    I too avoid hand sanitizers and anti-bacterial soaps for the same reason as you. I simply wash my hands with ordinary soap.

  6. A. Noyd says

    Sure, they kill 99.7% of bacteria, but what are we going to do when the resistant 0.3% becomes dominant, the sanitizer becomes useless, and few people have resistance to it because people have worked so hard not to build up immunity?

    Right? I mean, that sort of thing is appropriate for hospitals where they really do need to minimize the amount of bacteria on things, but that’s all the more reason to minimize the casual use of disinfectants and avoid breeding superbugs.

  7. says

    @Marcus #1 – I believe you meant the Spanish Flu, which broke out in 1918 during WW I. That was unusual in that it tended to hit younger people much harder than older. It is believed to have been a H1N1 virus, similar to the 1976 swine flu, which older people had already been exposed to and thus were more likely to be immune. Because of the huge (for that time) global travel and the unsanitary conditions and deprivations caused by the war, the flu quickly became a global pandemic.

  8. says

    I believe you meant the Spanish Flu

    Yup – that.

    So why aren’t we getting whacked by stuff like that all the time? Global travel is even more common than it was in 1918.

    A year ago I was in Jeddah for a project and went through the hajji side of the airport, which is basically a huge open space where people from everywhere in the world congregate. I managed to apparently get 2 strains of the flu at the same time (I got moderately sick with something that came on very fast and then very sick from something that came on right afterward, though I’m not really sure how to tell them apart except that one made me feverish and vomiting while the first one just made me feel moderately shitty) So why doesn’t someplace like Jeddah airport or London Heathrow result in an epidemiological melt-down for humanity?

  9. sailor1031 says

    Mano: I’ll avoid them when they stop providing them in hospitals. As it is my wife, an ICU nurse, has tp sanitise her hands every time she leaves one patient’s room to go to another.

  10. sailor1031 says

    Well, based on what I’m reading here in comments one would have thought that those unsanitary conditions would have just increased everybody’s resistance to the disease. And what about those areas that hadn’t been affected by WW1 – i.e most of the planet?

  11. naturalcynic says

    I have seen from a few sources that airplane cabin air is unhealthy because it is too dry. If you are taking external cold air and heating it, but not adding enough moisture. Dry air temporarily damages the sinuses and the throat so entry of any pathogen becomes a little easier.

  12. thewhollynone says

    Right, at #6; my ENT advised me years ago to use a nasal spray, even just a saline solution, before the trip and every few hours on long trips. Of course, being allergic, I have very little resistance to respiratory infections and tend to get sick after plane rides.

    I’m with you, Mano; I like to drive if I can. Of course, that’s more dangerous than riding in a passenger plane, statistically.

  13. Mano Singham says

    Yes, I am willing to trade the increased risk in return for avoiding the frustrations of flying.

  14. says

    There are two likely reasons. First, influenza is very unstable, and can mutate rapidly: that is why this year’s vaccine will not be very effective against next year’s flu. Sometimes, these mutations cause the virus to become more benign. Sometimes, they cause the virus to become much more virulent and lethal. H1N1 seems to pop up every couple of years: almost certainly, the 1918/19 outbreak was a mutation that was significantly more deadly than variants that appeared before or since.

    Second, modern sanitation began to appear in 1864, when Louis Pasteur presented the germ theory of disease, and 1870, when Joseph Lister developed and promoted the use of antiseptics. For the rest of the 19th century into the 20th, it was considered a moral requirement to keep everything as antiseptically sterilized as possible as a way of preventing the typhoid, cholera and tuberculosis epidemics of the past. This obsession for cleanliness was, for a time, omnipresent in North America and Europe, and was spread by colonial powers to outlying regions such as Australia and India. People who were in their 20s when the flu hit were the first generation raised in these antiseptic conditions, and we know now that absolute antisepsis actually inhibits the immune system, making it more difficult to fight off infections. It is also notable that the flu in Europe, Canada and America also hit people from wealthier families harder: they were the families better able to raise children in antiseptic conditions.

    And, keep in mind that the war was fought among the colonial powers of Europe. Many drew troops and resources from distant colonies in Africa, Asia and South America. This meant colonial troops being summoned to the European theaters of combat who returned with the virus. Already poor sanitary conditions, in areas that had previously only rarely seen influenza and among people who had little immunity, proved to be extraordinarily lethal.

  15. colnago80 says

    Before using a sanitizer, one should thoroughly wash one’s hands. By the way, one should also use sanitizers on shopping cart handles.

  16. Wylann says

    I love flying! I just hate having to go through security, deal with airlines, and put up with the crowds in the terminals and on the planes. I work in the aircraft industry though, and get to do a fair amount of private flying (I have friends with airplanes).

    Unfortunately, by the time you get to the point where a small, privately owned aircraft is even remotely practical for a cross country trip, in terms of range/speed, you are looking at least into the half a million dollars or so range. Although, based on Mano’s criteria (6-hour or less car ride), one could get a very good, reliable, used aircraft in the $50k range that would shorten a trip like that to just a couple of hours. Even with that, it’s only moderately practical if it’s used a lot, and is really worth one’s time. Owning an airplane is a way of life, and an investment in that ‘lifestyle’ (for lack of a better word). Typically, one can spend several thousand dollars/year, at minimum, just in annual maintenance, for a single (reciprocating) engine airplane, and keeping one’s pilot’s license current.

    If there’s a local aero-club, that’s the way to go!

  17. anne mariehovgaard says

    how is it any better than simply washing your hands, which will never result in a resistant strain?

    The only hand sanitizers I’ve seen here (Norway) are alcohol-based. I really don’t think alcohol-resistant bacteria are more of a problem than soap-resistant ones. Anti-bacterial soaps on the other hand do more harm than good.

Leave a Reply

Your email address will not be published. Required fields are marked *