How Clean Is the Air on Airplanes Really?

How Clean Is the Air on Airplanes Really?

With COVID, our daily lives have become entirely different, and many things are not what they used to be. One of the things that has changed most significantly due to COVID is travel. Specifically, travel by air.


A few months ago, we wrote an article discussing travel during COVID, emphasising the importance of masks. In that article, we discussed how you can choose a suitable mask for your trip, how you can stay safe, and more. However, after coming across some recent news, we wanted to look at the air quality when flying and how it can impact our health.


Recently it’s come to light that the air quality within the cabin of commercial planes is far from healthy. In fact, it’s quite the opposite. Even if we disregard COVID, there are reasons why masks should become commonplace while flying. 


Interestingly, the air quality in the cabin of planes is often touted as being very clean and pollutant-free due to the frequency at which it is cycled. However, this isn’t entirely true, and there’s more to the issue than face value would suggest. 


Today we will take a deep dive into the air quality in aeroplane cabins. Firstly, we will look at the actual air quality during flights - including during take-off and landing. Secondly, we want to make a case as to why it’s important to keep wearing masks during flights, even if they aren’t required by law as they currently are in many areas. 


You may be surprised (as we were!) with just how unhealthy aeroplane cabin air is! So let’s just say this - after reading this article, we are certain you will be ensuring your mask is ready for flights even post-COVID.

Flight Filtration Systems

When COVID first became a global issue, many people were worried about flying. At first glance, flying seems one of the most high-risk situations you can be exposed to. Being stuck in close confinement with hundreds of other people for hours is undoubtedly a way for COVID (and other viruses) to spread rapidly!


Many articles were quickly released stating that this was not the case. For example, the FAA stated that the air in plane cabins is as good or better than in other indoor environments (1). National Geographic said similar (2), and many other news sources had similar stories. 


This is because planes are equipped with air filtration systems that constantly replenish and filter air through HEPA filters. As a result, the air is cycled between 10 and 30 times per hour (3), and this should mean, in theory, that the air within aeroplane cabins is immaculate.


However, this is not true. We will look at the issue in more depth soon. However, before getting there, it’s worth discussing the problem with these flight filtration systems.



The Issue

Being inside the cabin is only part of a journey. If you’ve travelled before, you’ll know what we mean. There are often hours spent in the terminal at different stages of flight. Customs, waiting rooms, baggage claims, and check-in areas are all highly-trafficked. 


Further, there are restaurants, cafes, and other businesses in operation. These can contribute significantly to indoor air pollution with coarse, fine and ultrafine particles. On top of this, restaurants and cafes are a big source of VOCs (volatile organic compounds), pollutants linked to various issues (1).


Secondly, filtration systems are not always active, even once on the plane. On most airlines, the crew will not activate the system until airborne. While this wouldn’t cause an issue if we were only on the aircraft for a few minutes before taking off, this rarely happens.


We find ourselves boarded and waiting for thirty minutes more often than not. If there are technical issues or late passengers, this time can be extended even further. This becomes an issue because we are sharing air with hundreds of other passengers for this period that is not being circulated at all.


On top of this, the circulating air in the cabin is not as clean as we think. This makes a case for wearing a mask during flight. Let’s discuss the reality of in-flight air quality.


In-flight Air Quality

As we alluded to, even the air quality during flight isn’t great - quite the opposite!  What prompted this article was the recent trend of individuals taking air quality monitors onto commercial flights and recording the results. While we’re unsure where the trend started, many articles and Twitter threads have come to light showing the truth about cabin air. 


One Twitter thread (1) showed that during a flight from Fort Wayne to Chicago, carbon dioxide levels reached as high as 2351ppm. While this recording was done using a consumer-level carbon dioxide monitor, it shows a concerning issue. Levels of CO2 this high have been linked to various issues, including decreased cognitive performance (2).


Outdoor carbon dioxide levels are around 400ppm (3), and even relatively minor increases in CO2 from 600ppm to 1000ppm can significantly impact cognitive performance and overall health (4). With in-flight levels often far exceeding 1000ppm, we can see that an issue is becoming rapidly apparent. 


This is especially an issue during long haul flights, as concentrations lower than 5000 (but above the ambient levels) are not recommended for longer than eight hours (5). Exposures over this time can begin to have pronounced impacts, which is a big issue with current cabin air quality levels.


Humans cause this stark increase in CO2 levels. On inhalation, we breathe in ambient air, air which is about 78% nitrogen, 16% oxygen, 4% carbon dioxide and 0.9% argon (6). However, this composition significantly changes on exhalation, with our bodies changing 5% of the oxygen we breathe in to increase CO2 levels by nearly 40,000ppm - 4%!


Coupled with the fact that we inhale around 0.35 litres per breath and breathe 12-20 times per minute (at a resting rate), carbon dioxide in the air rapidly increases. Add to this the fact that hundreds of people are in a contained environment, and you quickly have exceedingly high CO2 levels. 


Another Twitter user showed that CO2 levels in the plane cabin during boarding and taxiing can reach as high as 3788ppm, an amount far above what is considered healthy for humans. At these levels of CO2, many people begin to have headaches, experience poor concentration, and nausea may even be present (7). 


While humans will inevitably increase the CO2 levels in enclosed spaces due to how our respiratory systems work, high levels like this are unacceptable - even if they are only during taxiing and takeoff. While levels will decrease once airborne, CO2 during flight is never at ‘safe’ levels. 


Another Twitter user found that even during flights when the HEPA-filtered HVAC systems are in use, CO2 levels can be far higher than we consider acceptable. For example, during a Delta Airlines flight, CO2 was found to be over 1500ppm (8). This is three times higher than ambient CO2 levels and can lead to various issues.


Finally, while less relevant, Dr Ed Tse was on an Air Canada flight when one of the engines stopped working. Since the HVAC systems are run on the engines, this caused the system to lapse and stop working. As a result, CO2 levels as high as 4900ppm were measured (9)!


While this is an exceptional circumstance, it’s worth noting because it shows the importance of being prepared. In this case, that means ensuring that you always bring a mask while travelling.



CO2 Isn’t the Only Issue

While this might seem contradictory to everything we’ve discussed so far, we are well aware that most disposable facepiece respirators and masks cannot filter gases such as carbon dioxide. So while CO2 levels this high do need to be addressed, this is the airline’s responsibility.


Therefore, although CO2 levels are concerningly high during flights, we see a bigger issue. This is the fact that CO2 levels represent the amount of ‘recycled’ air in the cabin. In other words, higher CO2 levels mean that we are breathing more air that other people recently exhaled.


Despite countless articles discussing how clean aeroplane cabin air is due to the constantly cycling air filtration systems, carbon dioxide levels found during the flight process indicate about 0.2-0.5%(1) of the air you breathe on an aeroplane was exhaled by another passenger. 


Put simply, the air you are breathing in flight, especially during boarding, was recently inside another person. That air is not fresh nor clean. When we begin to consider the implications of this, the issue becomes very concerning.


If we are inhaling air that was recently exhaled by another individual, that also means that we are inhaling a wide range of airborne particles that those people exhaled. This can include but is not limited to expelled respiratory particles that can contain viruses, among other particles.


Even though these larger particles don’t stay airborne for long, the proximity of seats in a plane cabin means that they don’t need to be airborne for longer than a couple of minutes to be inhaled by a nearby person. 


Due to COVID, we are now more aware of how easily airborne diseases can spread. However, more than just COVID can spread this way, and sicknesses can quickly spread in a cabin where masks aren’t required. Breathing this ‘recycled’ air can be equated to drinking water that someone recently spat out - we doubt you would want to do that!


Even though we are breathing the equivalent of spat-out water, very few people are concerned about the air quality during flight. We believe this is simply due to a lack of awareness because as soon as we learnt this fact, we decided that we would never fly unmasked again!


Flight Filtration Systems are Not Entirely Effective

Flights do have filtration systems in place. These systems are even highly effective - far more effective than those found in most offices, warehouses, homes, and other indoor areas. However, the issue is not that the systems aren’t effective but that they simply aren’t designed to handle the number of passengers that modern planes carry.


This is what leads to such exceptionally high CO2 levels in flight cabins. Unfortunately, despite much of the air being drawn inside and fully replaced every few minutes, the systems don’t keep up with modern travel.


Another issue is that while cabin air is constantly cycled (every three minutes (1)) and goes through HEPA filters to remove coarse, fine and ultrafine particles, this air is not filtered immediately. This effectively means that passengers breathe up to 0.5% ‘recycled’ air from someone nearby.


This problem is compounded when we consider that flight filtration systems are not active during taxi, takeoff and landing. There is often a thirty-minute wait when boarding a plane as the crew prepares and other passengers board. During this time, there is no air circulation or filtration active.


This issue was highlighted when another traveller recorded the carbon dioxide levels on a Southwest Air flight while boarding. The recorded levels were 3788ppm (2), or around 0.38% of the air in the cabin. Since no filtration is occurring due to the plane’s systems being inactive, this also means that the particles exhaled alongside that CO2 are still present and likely airborne. 


Why Wearing a Mask While Flying Is Essential

By now, we hope you can see why we believe masks during flights are essential - regardless of the current laws and situation surrounding the pandemic. Although many airlines still require that masks be worn currently, COVID is far from the only problem with aeroplane air quality. 


Since expelled respiratory particles are prevalent in flight, airborne viruses and diseases can also spread this way. Even if many of these aren’t as severe as COVID, no one wants to get sick intentionally - deciding not to wear a mask during flight is knowingly exposing yourself.


Even if you aren’t worried that sicknesses can quickly spread this way, the thought of breathing in the air that others have recently expelled is, simply put, disgusting. Since removing these expelled particles from your breath is as easy as wearing a mask, we highly recommend you consider wearing a high-filtration mask the next time you fly.


Although many of us are looking forward to the end of mask mandates - we are too! - there are some places where we hope masks continue to be worn. One silver lining of the COVID-19 pandemic is that it has drawn attention to the importance of mask-wearing and even allowed the practice to become socially accepted, something that it wasn’t before.


However, it has also led to many of us believing that COVID is the only reason we need to wear masks. While COVID-19 is the most pressing reason currently, there are many other reasons to wear a mask. One of these reasons is to prevent the spread of non-COVID sicknesses, especially in contained environments such as in a plane cabin.


Further, many of these issues are present not only inflight but also before and afterwards. For example, while airports tend to have better air quality (1) than flights, there are still air quality issues to be concerned with. Due to the large number of people aggregating in a confined space, alongside restaurants, cafes, and other businesses operating, air quality within passenger terminals is also an issue.


Next time you take a trip by aeroplane (or any other form of public transport, as trains and buses are even worse due to their often lack of filtration systems), make sure to wear a mask. You never know what it will protect you from, but at the very least, you can rest assured knowing that you are safe from the exhaled particles of others.



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