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From a pilot: is the air on airplanes actually clean?

We’ve all been there when flying – sitting in that comfortable middle seat, knees jammed against the seat in front, a baby crying nearby (always), and the guy across the aisle from you is coughing (or worse).

Our internal alarm bells sound off, and we wish we were a thousand feet away from this person instead of being trapped in a metal tube with them.

Airplanes were not designed for social distancing (obviously), which may leave you wondering just how safe it is to breathe the air onboard.

Airlines repeatedly like to tout the freshness of their air, with claims like “the air onboard is refreshed every 2 minutes”, but is this true?

Related: What is the Risk of Catching COVID-19 While Flying? How Can You Mitigate It?

Where does the air blowing through your vent while flying on an airliner come from?

Rumor has it that the cabin air on airliners is simply recirculated, but this is not true. The air actually comes mostly (>50%) from outside the aircraft, and is virtually contaminant-free. The rest is pushed through HEPA filters.

How does the air conditioning work on an airliner?

Simply, it comes from PACKs.

What are PACKs? Not something you bring to a picnic, PACK stands for:

  • Pressurization
  • Air
  • Conditioning
  • Kit

PACK is basically a fancy name for complicated jet air conditioners. It’s job is to take hot, pressurized bleed air from the engine’s compressor section and cool it down to usable cabin temperatures, as shown below.

It’s interesting to note that this air can be as hot as 500F before PACKs work their magic. As a pilot and passenger, I’m very thankful for that.

The outside of a jet engine
Outside vs inside of a jet engine
The inside of a jet engine

Of the air provided to the cabin, 50-90% comes from these PACKs. The rest is pulled from the cabin and run through HEPA filters before being combined with the PACK air in the air mixing unit.

The resulting air is 99.97% free of contaminants, and thus far cleaner and safer than the air in a supermarket and even in most people’s homes.

What is a HEPA Filter and what does it do?

HEPA stands for High Efficiency Particulate Air. These filters capture 99.97% of particles (bacteria, fungi, and viruses) 100 nanometers and above in diameter. COVID-19 is approximately 125 nanometers in diameter, which fits perfectly in the HEPA Filter’s zone of maximum efficiency.

This ultimately means there is virtually no chance of the virus being transmitted through the air system of the aircraft.

What regulates the flow of this super clean air? What about that guy coughing across from me?

There is another nice term for a system that is relevant for us and the cleanliness of the air while flying – the Environment Control System (ECS). The ECS monitors and controls air quality, temperature and pressure by directing the PACKs, outflow valve, and other pneumatic valves and fans.

The ECS also ensures that airflow inside the cabin is constantly flowing from top to bottom (at about three feet per second) and subsequently removed through the floor. This airflow is optimized to prevent longitudinal movement, meaning there is no spread between your row and the one next to you. This means that the air from that guy coughing across from you never gets the chance to visit you, especially in today’s face mask-required environment.

From the floor, air flows through ducts to the outflow valve, where it is sucked out of the aircraft continuously in order to maintain the correct pressure in the cabin. As a result, the cabin air is completely renewed with this fresh air every 2-4 minutes. For comparison, air in hospital rooms and classrooms is renewed about every 10 minutes and about 20 minutes in offices, and we already know it’s generally not as well filtered in the first place. Ew.

So yes, the airlines aren’t lying to you!

This is where the air coming out the vents comes from
Where does the air come from?
Why have I gotten sick on previous flights, and what has changed since?

You’ve most likely gotten sick by touching contaminated communal surfaces (such as tray tables) and then touching your nose, mouth, or eyes.

To prevent this, airlines are now using consistent techniques to clean these high-touch points. Almost every major (US) airline uses electrostatic spraying or disinfectant fogging between each flight.

One notable exception is Southwest, which cleans the interiors overnight for 6 hours, but not between flights. Mask wearing is now required on every airline and in nearly every airport.

This means the chances of being able to transmit the virus into the air or onto a shared surface in the first place are very low. Airplanes and airports have never been cleaner!

That’s nice and all, but does it all work?

Though I can’t speak for every airline, the one I work for (the best one, remember?) has had almost no reported transmissions from onboard. With a 90% testing rate of employees, we have a much lower-than-average rate of infection than the general public.

So, does it all work? As they say, the proof is in the flying… uhh… pudding… uhh… COVID tests?

By the way, if you would like to learn more about traveling to Europe, make sure to read How to Travel to Europe from the US During COVID-19 Travel Restrictions.

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4 Comments

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