Is the air on a plane safe & clean?
Yes, the air on an aircraft is clean, filtered and perfectly safe.
The entire air within the aeroplane cabin is replaced with fresh air approximately every five minutes. The air that is recycled within the passenger cabin passes through a HEPA filter which filters out almost all viruses (including Covid-19) and removes over 99% of bacteria.
How much of the air is fresh?
It varies from aircraft to aircraft, but at any given time approximately 60% of the air within an aircraft is fresh compared to 40% recirculated / reused air. On many aircraft types, the cockpit and therefore the pilots get 100% fresh air.
What filters the aircraft air?
Most aircraft use High-Efficiency Particle Filters (HEPA) to filter the recirculated air. These are the same filters found in hospitals and kill more than 99% of bacteria and stop particles which can carry viruses.
How air on a plane works…
The outside air temperature at the plane’s cruise altitude (approximately 35,000 feet) is as cold as -65°C / -85°F and is so thin that it doesn’t hold enough oxygen for humans to breathe. Therefore, an air conditioning system is used to provide air to passenger cabin which ensures a breathable and comfortable cabin environment for the passengers and crew.
This pressurised air is regulated by the Environmental Control System and Air Conditioning ‘Packs’. The process of pressurising the aircraft starts with air entering part of the engine. Before some of the air goes through the engine combustion process (where air mixes with fuel and ignites to produce thrust), it is redirected into the aircraft’s ‘bleed’ system. This basically means the air from the first part of the engine is fed into various aircraft systems such as the air conditioning and anti-ice systems. This air has been compressed through the initial stages of the engine and therefore it needs to be cooled down.
Once the air has been cooled to the correct temperature, this fresh air which has been compressed, is directed to the recirculation bay where it is mixed with air that has already been fed through the cabin. Once the two sources of air are mixed, this mixed air is directed to the aeroplane cabin for passengers to breathe.
Recycling of Air
The air then disappears under the floor towards the cargo hold. Some of the air is again mixed with the fresh air whilst the rest leaves the aircraft via the ‘outflow valve’ which is normally found at the rear of the aircraft. The amount of air entering the aircraft is a fairly steady rate; it is the amount of air which leaves the aircraft by the outflow valve which dictates the pressure of the passenger cabin (typically about 6-8psi). The cabin is typically pressurised to an altitude of 8,000ft (see our article on why planes fly so high).
The key point is that the majority of the air is ‘fresh’ (i.e. hasn’t previously been in the passenger cabin) and is also filtered to remove contaminants prior to being distributed to the passenger cabin.
Am I more likely to get ill from being on an aeroplane?
You are at no more risk of getting sick from being a passenger on an aeroplane than you are at being at any other large gathering such as bar, or cinema.
Being on an aeroplane is the equivalent of being in an enclosed space with lots of people except that the air within an aircraft is heavily filtered unlike most other comparable examples. There is a risk of a disease or virus being passed on, but it’s no more than any other enclosed space and arguably less as the air is effectively filtered.
Think of going to a concert, sporting event or even a busy bar. If you are within close proximity to someone who is ill with contagious disease or virus, you are more likely to catch it. However, if people are wearing appropriate personal protective equipment such as face masks, the distance of travel of any contaminants is significantly reduced.
Another point to consider is that the air on an aircraft is dry with low humidity. This dries out the mucus membranes within your nasal passage and this increases susceptibility to virus transmission. However, again, as the air is filtered, the chances of a virus being present in the first place is low.
So, yes, the risk is higher than if you are sat at home by yourself, but arguably safer than a crowded enclosed space such as the cinema.
This article was written by a current airline pilot who has experience as a Training Captain, Pilot Mangement, Wide Bodied and Narrow Bodied Aircraft over Long Haul & Short Haul Operations.