Last Updated on December 13, 2021 by tripcentral

Those of us who have done a number of trips can probably remember getting a cold or flu after travelling.  The most memorable part of the journey was your return flight, and so it’s often blamed as the cause of getting sick.  There would have been many places throughout your journey where the potential for infection could be transmitted from one human to another, but it was not due to recycled air on board.

Better than most Operating Rooms at 10-12 times per hour or more

People think because an aircraft is pressurized, that the same air is recirculated during the flight.   In fact, on jet aircraft, the air is replaced ten to twelve times per hour.  Existing operating rooms are required to replace air six times per hour, and new facilities are required to replace it twelve times per hour.  Air Canada reports replacement every 2-3 minutes.

Fresh air flows into the airplane fuselage and mixes with air recycled in the cabin.  Obviously, it is not possible to bring entirely fresh air in, but the consistent flow of fresh air in and venting out mixes with the recycled air to maintain freshness.  When you reach above your head to open the air vent in the ceiling, you can feel the coldness of the air.  In part, this is because a portion is fresh air coming from the chilly outside.

Here’s a video that explains the full air circulation on aircraft.  If you can put up with the computer-generated voice, it offers a thorough explanation of how the air is circulated on an airplane.

High Efficiency Particulate Air (HEPA) Filters

Jet aircraft are equipped with HEPA filters that are also used in hospitals, Dyson vacuum cleaners and your home furnace, to name a few.  They cycle air every few minutes and capture 99.97% of airborne particles greater than 0.3 microns in size. A human hair is a whopping 20 microns! We asked Air Canada how long HEPA filter technology has been in use on board their aircraft.  We were curious to see if this was only on new aircraft or something that was installed after COVID or even SARS.

Turns out HEPA filters have been used on board jet aircraft since the early 1990s.  We asked if there had been any improvement of cabin air quality since then.  Air Canada responded saying that the biggest improvement in cabin air quality was the introduction of the 787.  The composite material does not rust which allowed for higher humidity levels, but this has more to do with reducing dehydration than particle reduction. 

The 80-90 seat Q400 turboprop has HEPA filters installed and the Canadian Regional Jet (Bombardier) uses 100% fresh air with no recycled air.
Notably missing from the list of aircraft with HEPA filters is the turboprop commuter fleet (Dash 8) used for short one-hour journeys, although after-market filters are now available for installation by airlines.

Here is a video provided by Air Canada on how the HEPA filter works

Human to Human Contact spreads infection

It’s not the airplane.  Or travel in and of itself.  While travel can spread geography of infection it does nothing to accelerate actual transmission between humans.  The genie is out of the bottle in terms of geographic spread of the SARS2 Coronavirus.  The asymptomatic spread of this infection is what makes prevention by travel bans a futile exercise.

Only by reducing human to human contact, whether in your local community, or anywhere, will the rate of transmission of this virus slow.  HEPA filters, temperature checks, mask wearing, fogging aircraft, and more vigilance in cleaning between aircraft turnaround will all help reduce the spread of infection while flying.  It’s the human behaviour that is harder to control, and while we cannot control others, we can control our own behaviour.  This includes wearing gloves while touching screens or while visiting the onboard washroom.

More likely reasons people got sick after a trip

Lack of sleep is a big factor in diminishing one’s immune system.  If you stayed up late the night before a trip, got up in the wee hours of the morning for an early flight, or flew transatlantic without sleeping, this will affect your ability to fight off infection.  Replenishing lost sleep is important – read our blog on reducing jet lag.

In “normal times” we were not thrilled about getting sneezed on by the person next to us on a plane.  Or, the constant din of coughing sounds you heard while flying.  These experiences are history now with temperature checks and pre-screening questionnaires.  In the past, you’d lose all your money if you cancelled due to a cold or feeling under the weather.  Liberal change policies and ‘cancel with credit’ has eliminated the need to soldier on while not feeling well.

If you were handed an iPad for entertainment on a flight in the past, it was often a greasy mess of fingerprints – one could only imagine what was on those iPads.  Beyond the flight, you were travelling exploring cities, eating in restaurants (and touching menus), visiting sketchy washrooms in private establishments, having a drink in a pub, using public transit – double-decker buses, rail, taxis or visiting busy indoor places such as museums and shopping malls.  How about lining up and knocking elbows at buffets?  But of course, the most memorable time was the few hours on the return flight home which often “got the blame” for the cold or flu.

Other Articles

The Truth About Recirculated Air on Airplanes

https://www.washingtonpost.com/opinions/2020/05/18/airplanes-dont-make-you-sick-really/

https://pubmed.ncbi.nlm.nih.gov/19076326/