So you’re flying to London on the Dreamliner, you’ve just been served a hot meal and a glass of wine, and you’re putting your Covid mask back on, hoping to catch a few minutes of sleep while you trundle over the Atlantic ocean at 35,000 feet.
Let’s face it, airline passengers rarely give a second thought to the air they breathe while on an airplane — other than twisting that little doohickey on the ceiling to adjust the air ventilation.
They are clearly not aware, that companies such as Collins Aerospace have decades of experience in designing and manufacturing cutting-edge systems to keep cabin air clean.
Now that people are beginning to fly again during Covid-19, cabin air quality is now top of mind for many.
A recent Harris poll found that “even after the government signals that Covid-19 is abating … only about half of Americans (49%) think they’ll be ready to fly” within the following six months.
From its first environmental control system for the North American F-86D SabreJet in 1949 to its more electric ECS for the Boeing 787, Collins Aerospace has been providing passengers with safe cabin air for more than 70 years.
During the coronavirus, however, its ventilation and sanitation that have become key areas of focus.
“What most people don’t realize is that the air delivered to an aircraft cabin is of very high quality and has been for many years,” said Lee Annecchino, vice-president for Air Management Systems at Collins Aerospace.
“In fact, the air supplied to a large commercial aircraft that uses a HEPA filter in its ECS can be as clean or cleaner than the air in a hospital operating room.”
The keys to clean cabin air include high rate of fresh air flow, High Efficiency Particulate Air filters, commonly called HEPA filters, and the design of aircraft airflow distribution.
The biggest factor in cabin air quality is the inflow of fresh air.
Aviation regulatory authorities such as the Federal Aviation Administration and European Aviation Safety Agency require a minimum rate of 0.55 pounds per minute outside fresh air flow per occupant.
In a large commercial passenger aircraft, that means a typical environmental control system may replace the air occupying the cabin every 2 to 3 minutes — 20 to 30 times per hour.
By comparison, the general guidance on fresh air inflow for your office building is only 4 changes per hour.
In most of today’s environmental control systems for large commercial aircraft, such as Collins Aerospace’s ECS for the 787, the fresh air inflow is mixed with recirculated cabin air.
The recirculated cabin air is passed through HEPA filters to remove particulates such as dust and mitigate the transmission of bacteria and viruses. HEPA filters have a higher filtration efficiency rating than “N95” respirators and are the same filters used in hospital protective environments.
In addition to filtering and regularly replacing cabin air, aircraft environmental control systems also distribute air flows from ceiling to floor — not front to back. This helps reduce the spread of unfiltered, contaminated air.
While all three of these elements have been common to aircraft environmental control systems since the 1990s, Collins Aerospace is now looking for ways to use the cabin air distribution system to further increase cleanliness in response to Covid-19, while reducing the burden on airline maintenance personnel.
Methods under consideration include using the air distribution system to inject cleaning agents such as hydrogen peroxide or ozone into an empty cabin between flights, Annecchino said.
The study found the risk of aerosol dispersion — transmission of the virus through the air — was reduced 99.7% thanks to high air exchange rates, HEPA-filtered recirculation and downward ventilation.
Investigators looked at the impact of an infected passenger on others seated in the same row and those nearby in the cabins of Boeing 767s and 777s.
Those two aircraft types are widebodies typically used for long-haul flights where a virus would be expected to spread more easily, USA Today reported.
To test the exposure risk for passengers sitting near an infected person, researchers released fluorescent tracer aerosols representing the droplets released by exhaling or coughing and looked at the impact on multiple “breathing zones” throughout the aircraft.
In total, more than 11,500 breathing zone seat measurements were taken with releases from 46 different seats.
Other reports have found people became infected with coronavirus on flights, perhaps when they took off masks to use restrooms, CNN Travel reported.
“Testing did not include substantial movement throughout the plane or in the airport, lounge or jetway, where air change rates and human interactions will vary,” the researchers added.”
Similarly, the mannequin remained facing forward, uncertainty in human behavior with conversations and behavior may change the risk and directionality in the closest seats to an index patient, especially for large droplets.”
(Sources: Collins Aerospace, USA Today, CNN Travel)