A study by the US Department of Defense, released on Thursday, has found that the risk of aerosol exposure on airplanes is “minimal”. The study says the risk of transmission of cornanvirus on-board can be reduced with the use of HEPA air filters, refreshing the cabin air every two minutes and ensuring top to bottom airflow to protect all passengers.
United Airlines, one of the worst-hit airlines due to the pandemic, tweeted about the study’s results on Thursday: “The results are in: Your risk of exposure to COVID-19 is almost non-existent on our flights (yes, even on a full flight).”
The objective of the study was to determine COVID-19 risk analysis planning with respect to optimal flight capacity, determining risk under different seat configurations, optimising strategies for boarding and de-boarding and determining which contact tracing strategies would be necessary in case a passenger tests positive soon after landing.
The study claims to be the largest such that has conducted aerosol experimental validation testing and involved eight days of both in-flight and ground tests on Boeing 777-200 and the 767-300 aircrafts.
The study says that aerosol exposure risk, even on long-duration flights, is minimal. It is highest when the individual is seated in the row of the index patient. Further, rows in front and behind the index patient have the next highest risk of being exposed to aerosols on average.
To conduct this research, tracer aerosols, that simulated an infected passenger, were released in multiple rows and seats in order to determine the risk of exposure and penetration into breathing zones of nearby seats. Overall, over 300 aerosol release tests were performed.
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What about masks on board?
For the purpose of this study, researchers took into consideration surgical masks, which are most likely to be distributed when other kinds of masks are not available or if a passenger has not brought a mask. Therefore, researchers used the standard three-pleated masks supplied by United Airlines.
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So what does the study tell us?
The study assumed that there was just one infected person on the plane with 100 per cent capacity on a 12-hour route. When this person is wearing a mask, the study says that 0.003 per cent of the air particles within the breathing range of this person are infectious. Significantly, researchers found that a large number of flight hours are required to get infected. It says that a minimum of 54 hours of flight time is required to get infected when sitting next to an infected person in the economy section of the 777 aircraft.
As per the International Air Transport Association (IATA), globally, in 44 COVID-19 cases, transmission is believed to have happened on an airplane, during a time when 1.2 billion passengers have travelled.
What are the possible reasons for low inflight transmission?
As per a joint publication released by Airbus, Boeing and Embraer, some reasons why the risk of transmission in an airplane may be low are aircraft airflow systems, HEPA filters, the downward flow of air and the high rates of air exchange. Further, passengers wearing masks “adds a further and significant extra layer of protection”.
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