How clean is the air on planes?

The coronavirus epidemic has served as a reminder that global health priorities include access to clean air. While industrial pollution has long dominated headlines, COVID-19 shifts the focus to indoor pollution. The quality of indoor air—the direction in which it moves, the extent to which it allows or prevents germs from dispersing or disappearing—can be the difference between staying well and becoming ill. Among the interiors that have been frequently identified as possible infection hotspots (churches, nursing facilities, and cruise ships), airline cabins are a source of concern.

As a result, it’s a pleasant surprise to discover that the air inside a plane is much cleaner than you may believe. The air you breathe in commercial airplanes is significantly cleaner than the air in restaurants, bars, supermarkets, even your best friend’s living room, owing to HEPA filtration and excellent circulation. Here are some reasons why you should not be afraid of the air up there.

How airline air is purified

Commercial airplanes are equipped with HEPA (High Efficiency Particulate Air) filters in the majority, but not all, cases. This means that the airflow on HEPA-equipped flights “mirrors the laminar airflow found in an operating room, with little or no cross-flow of air streams,” according to Dr. Bjoern Becker of the Lufthansa Group of airlines. “Air is pumped into the cabin from the ceiling at a rate of around a yard per second and then sucked out again beneath the window seats.”

Around 40% of the air in a cabin is filtered using this HEPA technology; the remaining 60% is fresh and piped in from outside the aircraft. “While the airplane is cruising, the cabin air is totally changed every three minutes on average,” Becker explains.

According to Tony Julian, an air-purification expert of RGF Environmental Group, certified HEPA filters “block and capture 99.97 percent of airborne particles larger than 0.3 millimeter in size, as how HEPA works in the best air purifiers you can find.” Perhaps counterintuitively, the efficiency of these filters rises as the particle size decreases. Thus, while the inhaled globules carrying SARS-CoV-2 may be quite small, HEPA filters efficiently filter out the great majority.

“Typically, the number of particles in the air is very low; the plane is almost like a clean room, due to the high level of ventilation and the fact that there are very few sources of particulate generation within a plane,” says Liam Bates, CEO and co-founder of Kaiterra, a manufacturer of air-quality monitors. “[Planes] are in fact safer than almost any other enclosed area.”

HEPA filters are not installed on older airplanes or small aircraft with less effective filtering systems. However, even the most sophisticated filters cannot capture every virus particle carried onboard, and airlines, their personnel, and passengers can impact their performance.

How trustworthy are filters?

The 99.97 percent filtering efficiency of HEPA is reassuring, and airline executives rely on it. However, the primary flaw with those systems, according to Bates, is that the “filter guarantees only the quality of the air that has passed through it. If the air someone breaths has not passed through that filter, those numbers are irrelevant.”
That is why, in addition to having effective filters, airline cabins require effective passengers. This requires that everyone onboard wear a mask.

This is due to both the established protective features of masks and the fact that HEPA filters and rapid-air circulation do not function optimally until the plane is airborne. This means that the sometimes interminable interval between securing your seat and takeoff (or between landing and disembarking) is the most likely moment for you to inhale a COVID-19-infected cloud of air. That stale, heated air you occasionally detect when a plane is on the ground, sitting at the gate or idling, could indicate that those filters are not getting enough circulation.

As is the case with most technology, “HEPA filters should be inspected on a regular basis and updated as necessary,” Julian advises. For example, holes in the filters or issues with the seals will reduce their efficacy. Each manufacturer of HEPA filters recommends a maintenance schedule for their equipment, and most airlines change it more frequently. Even if an airline changed filters less frequently than recommended, the International Air Transport Association reports that while airflow through the filters may be reduced, their particle-trapping capacity would remain unchanged. Contrary to popular belief, dirty filters can be more effective than clean filters.

Why is masking necessary?

When we cough, sneeze, or speak, minute (and occasionally noticeable) droplets of saliva exit our mouths. While the larger ones fall fast to the ground (or an armrest), the tiny ones can float in the air. While the science around SARS-CoV-2 is still advancing, there is now some indication that the virus contained within those tiny droplets is infectious.

Wearing a mask the entire flight keeps part of the airborne saliva—and whatever viruses it may contain—to yourself. There is evidence that wearing a mask protects others around you and decreases your risk of infection. Consider wearing a mask similarly to stowing your laptop before take-off: it reduces the likelihood that anyone will be struck in the face with something harmful due to air turbulence.

There is no law in the United States requiring flying passengers to wear masks. Each airline in the United States has imposed its own mask policies (here are the ones for American, Delta, and United). There are several accounts of airlines strictly implementing them (Delta banned over a hundred barefaced rebels and returned to the gate to eject passengers), ignoring them, or placing the onus on passengers to monitor those sitting around them. However, there are reports of people flying without masks (or wearing them incorrectly) and flight crews not enforcing the laws.

How screening may assist—or not assist

Airports and airlines in the United States are implementing additional screening procedures to prevent possibly infectious people from boarding passenger planes. Some rely on travelers’ honesty and ethical behavior, such as airlines that require passengers to confirm that they have been free of COVID-19 symptoms for the previous 14 days during check-in.

Even if every passenger is truthful, other passengers are still at risk, as approximately 40% of COVID patients are asymptomatic, and many individuals in the disease’s early stages exhibit no symptoms at all. Certain airlines, like Qatar Airways, are requiring customers and personnel to wear masks and face shields. The mask safeguards others, while the face shield safeguards you (especially from the virus entering your eyes).

Numerous screening methods indicate that airports and airlines are serious about COVID-19, but experts note that such precautions are not necessarily grounded on scientific evidence. “While passenger temperature screenings give us the impression that we are doing something tangible to prevent the spread, the scientific evidence to date indicates that they are neither efficient nor effective at identifying COVID-19 patients or reducing the spread,” says Dr. Daniel Fagbuyi, an Obama Administration appointee to the National Biodefense Science Board with experience managing pandemics. Temperature checks using thermometer guns miss 30% of individuals who have fevers.

Methods for ensuring your safety during flight

When flying, the greatest danger may be the airport, boarding, and takeoff/landing experience. Individuals in close indoor proximity, who may or may not be wearing masks, could result in infection. Maintaining a six-foot (or greater) social distance while traveling to your gate, into your seat, or deplaning is probably more critical than anything else you can do (except covering your face).

If you really must fly, select an airline that adheres to its own precautionary policies. At the very least, you’ll be less bothered about being a mask enforcer. Alaska Airlines appears to be the most attentive US carrier about mask wearing as of mid-August 2020.

While Delta, Alaska, Hawaiian, and Jet Blue are keeping middle seats unoccupied for the time being, any COVID protection gained will likely come from fewer passengers, not from whether a stranger sits a few inches rather than a foot from you. A much-discussed Massachusetts Institute of Technology study published August 18, 2020 indicated that leaving the middle seat empty on airplanes reduced a passenger’s risk of getting COVID-19 by a factor of 1.8, however the paper has not yet been peer-reviewed.

On board, avoid prolonged contact with surfaces and thoroughly clean your hands before contacting your face (including your mask). However, Dr. Ken Perry, an emergency physician in Charleston, South Carolina, asserts that there is no reason to fly in a HAZMAT suit. “Rather than worrying about gloves and other devices, people would be much better off being meticulous with their mask wear.”

Scientists believe that the primary cause of COVID-19 transmission is no longer touching objects and subsequently touching your eyes, nose, and mouth with dirty hands. However, a new investigation on inflight transmission indicates that an asymptomatic person may have transferred the disease via toilet surfaces.

Airlines have enhanced their cleaning procedures, including the use of electrostatic sprayers to disinfect planes. Additionally, American Airlines will begin treating high-touch areas (seat backs, tray tables) with SurfaceWise2, a coating that is believed to destroy coronavirus for up to seven days.

Fagbuyi recommends wearing your mask as much as possible during flight. This includes abstaining from eating and drinking while in the air. While hand sanitizer is acceptable onboard, Fagbuyi recommends “washing your hands with soap and water once you get off the plane,” particularly before removing your mask.

And, while it may be uncomfortable, Dr. Joyce Sanchez, medical director of Froedtert and the Medical College of Wisconsin’s Travel Health Clinic, says covering up has no effect on your oxygen or carbon dioxide levels. “The vast majority of people, including those with severe lung and heart conditions, can wear them safely,” she explains.

As it turns out, the most effective technique to make the skies more hospitable right now is to conceal your smile.