HEPA is great on the plane. When it’s on. And it’s not always on



Diseases are not new, and airlines have for years been using methods of removing pathogens from the air, such as through the HEPA air filtration system (no one can seem to agree on what the A stands for— is it High-Efficiency Particulate Air, Arrestance, Absorber, or something else?). However, most people focus exclusively on an aircraft as some kind of sealed sardine can, churning stale air, when in reality they face the most danger before ever setting foot on the plane, as the airport itself is often overlooked as a virulent source of contagion.


This is with (mostly) good reason too, because as far as indoor spaces go, airports do tend to be the safest, often having high ceilings and powerful air filtration systems.  But people tend to let their guard down here, which is why you must be extra vigilant.  Beginning with the first step of airport life, security clearance, there are things you may do a little differently.  For instance, instead of placing your phone, wallet, keys, or other pocketable items in a bin, instead place them in your bag to minimise contact, as while bins are cleaned, domestically at least, it is still a busy place with many people in close proximity increasing the odds of transmission. Another good tip: if you’re traveling with food, keep it in a separate bag and place it in another bin, as this decreases the odds of security needing to open your bag.  


The most dangerous place, pathogen-wise, to be during this time is the bathroom.  As Coronavirus can be passed through bodily functions, and the flushing of a toilet can aerosolize these particles, wear glasses or a face shield and most certainly a mask. And wash your hands with hand sanitiser just in case. 


Hopefully by now you’ve made it to what should be the safest part of your trip, the aircraft.  But what exactly makes the aircraft safe, and what could you do to make it safer? Well, here are your answers, beginning with the strongest defense in the aircrafts arsenal.


While no one can seem to agree on the proper name of the aforementioned HEPA filter, many can agree that it is highly effective, as microscopic pathogens are absorbed into a cozy little filter where their cellular skins are eviscerated ferociously by UltraViolet Radiation.  This germicidal genocide operates with such efficiency that there is apparently only a .00001% chance of microorganisms may survive. This may be why not only airlines use it but every major hospital as well. 


HEPA not only filters onboard air, but brings in new air from outside, meaning all air within the system is replaced every three minutes. So in truth, you don’t breathe technically stagnant air while flying, although it sure feels that way. Delta partnered up with Georgia Tech to conduct a study on air quality and found that on average in-flight air is many times cleaner than air sampled in various indoor spaces.  


However, as effective as it may be, it is not perfect. With such a novel virus we can no longer count on HEPA alone to keep us safe, especially as it only operates in flight, leaving you most vulnerable during take-off, landing, boarding, and deplaning — which can be as long as the flight itself sometimes. Because HEPA is only effective when it’s on. And it’s not always on. 


There have been recent changes so that now before and during boarding and taxiing a smaller, low quality ventilation unit runs. United Airlines further led the charge for airlines to have the HEPA system turned on full blast the entirety of the time the plane is being used, meaning that there is now a much smaller chance of latent pathogens in the air than before.  


There’s also the matter of luggage under the seats blocking airflow. Here is a rather annoying video from United Airlines showing how the HEPA system works. You can see how they draw in the diagram the air going under the seats where it could be blocked by luggage.  Because the air blows down, this is not really that big of a deal, though I suggest keeping all bags in the overhead bin if possible. 


The most obvious thing you can do for protection is simply continue to wear a mask, at least for the foreseeable future. In conjunction with H.E.P.A. this can greatly increase your safety.







“But wait!” I hear you screaming, “People are still going to eat on the plane, with masks off, and even if the plane stops serving food what’s to stop people from bringing it on?” Well, great point. Many have floated the seemingly simple idea of staggering meals, serving every other row so not everyone is eating at once. But can you imagine being starved on a plane, exhausted from breathing through a mask and more irritable than usual, and finally the refreshment cart comes by and skips you? Many of us might respond with just an aggravated eye roll, but this would likely lead to a plague of Karens… 


So should you the traveller abscond from refreshments and accept your dismal fate? Not quite, recall once in the air, H.E.P.A works at 99.9% efficiency meaning that much of the air blowing down onto you is  not only fresher and cleaner than the air within an apartment or office building, but blows whatever pathogens may be floating around down to the ground.  Which means that if you’re in a row alone you would probably be just fine.  


There is a world of difference between probably and certainly. While that 99.9% may seem too good to be true, as it is clearly a lab result where all the conditions are perfect, surely in the real world dust could clog the system or some microbes could survive, and it is true there is some variance in the data.  The more realistic number, all things considered, comes in at a whopping 99.7%, as unless the system has been completely neglected, it’s still incredibly effective.  


The weakness here is not in the sanitation process, but rather in the intake, as there can be “air eddies” created like when in rivers the water flows backwards due to the shape of a shoreline, creating a whirlpool of sorts. 


However, every meal has its end and every beverage must go somewhere, which leads us to the largest vector of possible transmission beyond the airport itself — the airplane lavatories. Since the Coronavirus can be passed through our waste, wait at least thirty seconds to use the restroom after the person in front of you to allow these particulates to land, so you may wipe them away. This is not enough for Chinese airlines, which have requested all flight staff wear diapers so as to not have to venture into the lavatories at all.


And, speaking of wiping away, how exactly do airlines handle desanitizing surfaces? Well, prior to the pandemic, most planes would get a thorough six hour cleaning after retiring for the night, which, while thorough, would not stand up during a pandemic, so they changed their cleaning policies.  There are small variations amongst airlines, but the main difference is in how domestic and international flights are handled.  Mainly, domestic flights do not have as much time for as thorough a cleaning as international flights, meaning they are at a slightly higher risk.  On top of this, most international flights have another degree of safety in that many countries require proof of a negative test in order to enter the country. Domestic flights do not have this stipulation. 


Most flights will receive a fogging of disinfectant that is highly effective.  Rather than traditional misting, this process electrically charges the microscopic droplets of disinfectant making them repel one another and fly much farther, for much more coverage. This electric charge also helps the disinfectant cling to any surface, truly purging the environment.  When there is time, such as for international flights, a team of cleaners will board, opening every tray table, before a second team with super EPA approved wipes come and wipe down every surface that comes in contact with people. And many airlines now offer flyers complimentary disinfectant wipes. So they can do it all over again.


However, as Paul Scialla, the CEO and Founder of the International Well Building Institute, and Delos, a New York-based building health and safety company puts it “cleaning alone will not be an effective solution in stopping transmission, and even more importantly we know that any and all strategies need to be codified and verified.” Meaning, although these methods have remarkable capabilities removing the virus between trips, in the end it is an aerosolized virus that is still very capable of transmission due to the human element and our nature to make common sense not so common. 


Well, it was nice while it lasted — but the filled middle seat is back! Airlines couldn’t wait to sell those again (and to increase prices, and bring back all the extra fees that make flying more expensive than it need be). Many airlines had kept the middle seat empty in order to attempt social distancing in the sky (and also, seriously, they were hardly flying full during the pandemic). Did it actually help reduce transmission? Yes and no. It is true that this probably lowered the odds of transmission, however not by much. Because you still weren’t that far away from the next passenger. And, anyway, it will all seem like a dream when you’re next on a plane and it’s full to the gills.


To sum it up, airplanes are still the safest form of public transportation, although their mitigations are not foolproof, and at the end of the day, the burden of responsibility does still fall mainly on travellers.  


If you follow the protocols and wash your hands, wear your mask and/or a face shield, chances you will contract the virus are near zero. The airlines have also realised that the greatest weakness in their system is the passengers themselves. This is why multiple international airlines, spearheaded by Air France, are working together to develop digital wellness passports in order to keep those flying both screened and safe, closing the biggest loophole in the system.     



Well, it’s superclean now Photo provided by Wonderlust




Not all masks are created equal, and in order to protect you do not be surprised if you are turned away at the gate for having the wrong kind of mask!  While you probably won’t miss your flight, you may be required to wear the quite uncomfortable single use mask that would come with their complementary sanitation kits. While different airlines have different policies they often require that your mask doesn’t have an exhaust port. These make breathing easier, they also allow pathogens to escape, possibly infecting others. 


To really understand how well these systems operate, let’s look at when it has gone wrong and people have gotten sick. Vietnamese flight VN54, took off from London, March 1, 2020, en route to Hanoi carrying a total of 16 crewmembers and 201 passengers for a 10 hour long flight.  The date of this flight is very important as this was right as the virus was ramping up and before masks were mandatory, and hardly worn on planes.  No safety measures were in place. No wiping down tray tables, or seat blocking, only the HEPA system, which wasn’t on when the plane was on the ground. Of all 217 people on board, one walked on sick and 15 walked off with coronavirus.  


This means there was an infection rate of 6.9% when no one was taking any precautions. Not cataclysmic, but a bit like Russian Roulette. And in this case 12 of the 15 infected were near the one sick man, the others being the sick man himself and two people he came in contact with.  This shows the wonders and setbacks of the HEPA system as viral matter caught was terminated and did not apparently spread through the plane. The air flow was, however, not strong enough to carry the virus directly to the floor, instead letting it reach a few rows away.  


If masks had been worn this number would probably have dropped dramatically.