Air travel is touted to be one of the safest modes of travel out there. With the onslaught of the devastating Novel Coronavirus pandemic, it has left us in tenterhooks whether to go ahead with our travel plans or not, especially the long haul ones since they are considered high risk for virus transmissions. A popular myth amongst fliers is that one sick person on-board can transmit the Coronavirus to the rest, which is far from true. With precautions and advisories in place and assuming people adhere to them, air travel can be one of the, if not the most, safest mode of travel.
To understand the degree of transmission risk, let’s look at how air circulates within the cabin.
Air circulation inside an Airliner
Aircrafts fly at altitudes that are unsustainable for human life. Compared to the ideal conditions we have at ground, conditions up there can wreak havoc on human biological cycles. Hence it becomes imperative that aircraft air systems be designed to maintain the cabin pressure levels suitable for humans while at the same time keep the air fresh and at an ambient temperature. Here’s how it works.
The air outside the cabin is breathed into the engines which then flows into the compressor. After being compressed to a density safe enough for humans to breathe, this compressed air enters into what is called a ”mixing manifold”. The compressed air is hot and hence it needs to be cooled. This compressed air is then mixed with the re-circulating air from the cabin in the mixing chamber and passes through special filters known as ”HEPA” filters (more on that later). This filtered air then passes throughout the cabin via connecting ducts where the ceiling meets the sideboard. Half of the air is dumped overboard ensuring a continuous flow of air within the cabin.
High efficacy particulate air filters (HEPA)
HEPA filters are high quality aircraft air filtration systems of medical grade, touted to remove an astonishing 99.99% of airborne microbes and dust particles in air.
“HEPA filters are effective at trapping microscopic particles as small as bacteria and viruses” – IATA said in a paper, Cabin air quality – Risk of communicable diseases transmission, published in 2018
According to experts though, air filtration systems and HEPA filters alone cannot completely negate the risk of transmission. These filters are designed to only filter particles that reach it. Thereby the risk of transmission from unfiltered particles still lingers and that’s exactly why Coronavirus appropriate activities like physical distancing and donning a mask still needs to be followed.
Conclusions from certain case studies
Airbus tried simulating a highly accurate flow of air in an A320 cabin using CFD to detect the transmission of cough particles with people seated next to each other Vs people staying 6 feet apart. The result concluded the risk of transmission as lower in the former than the latter
Research by the US Transcom propagated that suspended air particles were rapidly diluted by the high exchange rates of air in a typical aircraft cabin. Tests in B777 and B767 proved that particulate matter was removed 15 times faster than in a home ventilation system and 5-6 times faster than a typical hospital ventilation setting.
Researchers at the Harvard School of Public Health have found that following Novel Coronavirus appropriate behaviour coupled with the aircraft’s ventilation systems resulted in a very negligible risk of transmission
Modelling the remaining risk
Manufacturers have developed a risk-management model which calculates the risk of Novel Coronavirus transmission and translocation by modelling the various steps and parameters in the curb-to-curb air travel journey. The objective of the model is to support government and regulatory bodies in making data-substantiated decisions when reopening air travel. This is timely and relevant as the first travel corridors are being discussed between low risk or “green” countries.
The evaluation quantifies the level of risk for each step and takes into account the various health and safety measures, such as wearing face protection and different testing and quarantine scenarios. In practice, the model displays several protection and screening strategies that can be activated on a chosen route and simulates the impact on lowering the overall risk through applying those measures.
Disembarking the light way
In response to pre-emptive passenger offboarding, experts are introducing a solution to ensure an orderly and safe way to disembark, avoiding crowding of the aisles and keeping everyone onboard comfortable. The solution is a novel lighting design based on simple traffic guiding principles: the scenario uses different cabin illumination combinations to indicate the rows which are designated to disembark next. The lighting scenarios complement the verbal cues given by the cabin crew to facilitate an orderly and rush-free departure from the plane.
Initiatives from major carriers
Qatar Airways became one of the first global carriers to implement the use of UV(ultraviolet) cabin systems by Honeywell. Clinical trials have proved the efficiency of UV light in successfully inactivating a number of airborne microbes when applied in the right doses. Also, The Doha based airline along with Emirates have been seen running massive PR campaigns boasting of fully vaccinated crews.
“We understand there will be some (aircrew) who cannot take a vaccine and we will look into accommodating them on a short-term basis where we can. However, we will review the future employment of those who are unable to become vaccinated and assess whether they can continue to be employed as aircrew with Cathay Pacific.” – a spokesperson for Cathay Pacific said last week.
“We are pleased to operate flights with fully vaccinated crew – a significant step in protecting our employees’ and customers’ health safety. We have been squarely focused on working very hard to ensure the safety of our staff and passengers since the pandemic broke out and this is another testament to our continued commitment.” – Ethiopian Airlines Group CEO Mr. Tewolde GebreMariam
The way forward
Despite all assurances, It will still take time before people overcome their fear completely. For this very same reason, awareness should be created regarding public safety on-board. With some positive signs of recovery, especially in countries with high rates of vaccination, a sustained global recovery will only be realized with an escalation of vaccination campaigns, the continued development of digital health passes, and coordinated and cohesive policy support from governments.