How do airlines and their suppliers ensure the passenger’s onboard experience is one which takes into account their complete wellbeing? In this, the second part of a comprehensive three-part series, Bernie Baldwin comes up for air and discusses how best to manage the cabin environment.

Suitably seated, next parameter where the passenger requires high quality the air in the cabin. Hygiene factors such as the temperature are controlled relatively easily, the humidity – or lack of – much less so.


CTT Systems has been balancing the levels of humidification for some time. Its lead product nowadays is an inflight humidification (IFH) system, Humidifier Onboard, developed after assessing the ways in which biological and physiological factors react to low humidity.

“An aircraft cabin is incredibly dry, often as low as 3%-6% relative humidity (RH) in a premium cabin,” explains Ola Häggfeldt, CTT’s sales director. “In the flight deck, there is almost no humidity, while in First and Business class, premium passengers enjoy leading comfort and best services, but those come with a price – a cabin climate more dehydrating than any place on Earth.

“The body’s natural moisture balance on a long-haul flight is therefore disrupted, causing dry air-induced fatigue, rapid degeneration of the immune system and impaired taste. It’s important to keep the immune system intact during a flight and, even more importantly, at arrival when entering the terminal building,” Häggfeldt remarks. “The RH required for a premium cabin is about 20%.”

Peter Landquist, CTT’s VP senior advisor sales, adds, “We could humidify the premium class up to 35%, maybe even 40%, but then you need a drying system too. It’s a trade-off, stop the dehydration process and still provide a lightweight, easy-to-install system and not take too much water because the idea is that an extra water tank to increase humidity should not be needed.”

Class Distinction

There is a big move across airlines towards Premium Economy cabins, again reducing passenger density. So are airlines asking for Humidifier Onboard in that cabin too? “Not yet,” Häggfeldt reports. “They’re more focused on first and business class. But if you’ve humidified those, you will indirectly increase the humidity in premium economy. With recirculation, premium economy might go to somewhere between 10% and 14%.

Finally, while CTT’s humidification products have tended to be on widebody or business aircraft, that may change, with aircraft such as the A321LR/XLR. “The trend to develop narrowbody airliners for intercontinental long-haul will drive humidification for premium cabin in this segment as well, It’s available already as a retrofit,” notes Landquist.

Not only does cabin air need the right humidity, it needs to be as fresh as possible, particularly in the wake of the Covid-19 pandemic. Passengers need to feel comfortable with the air passing through, not only for their physical wellbeing, but their mental health too.

Pexco Aerospace’s AirShield, which uses the air system’s nozzles to create protective air barriers in between and around passengers, has been drawing attention as a viable product in this area. It is now on the verge of certification.

In developing AirShield, Pexco had to determine the optimum airflow to enable the each air barrier to be effective. The company’s president, Jon Page, explains the methodology behind the tests to achieve that.

“The big thing we had to consider with AirShield was how airborne particles behave in a cabin full of people, with nobody wearing a face mask. To understand the scale of the problem, we modelled more than 60 million data points of CFD (computational fluid dynamics) to get a definitive picture of what was happening to airflow in the cabin on a particulate level,” Page begins.

“Our results found aircraft cabins to be highly efficient at exchanging and cleaning the air in considerable volumes. But our research also discovered that we could enhance performance by adapting the airflow around passengers using the existing vents. In doing so, we found we could restrict droplets from every sneeze, cough, or breath, as well as unwanted odours passing into passengers’ personal space, while doubling how quickly these particles are sent to the HEPA filters to be replaced by purified air.

“From the outset, we wanted AirShield to be easy to install and certify, which meant maintaining the existing air volume in the cabin but making it work differently,” Page continues. “We performed numerous testing procedures, including dB level, g-force, flammability, and laboratory fog tests. We also completed on-wing tests with American Airlines, Southwest Airlines, and Alaska Airlines. These tests, in real cabin environments, proved, without doubt, the advantages of the technology.”

Air Flow

Some passengers are averse to air flow directly onto their face, but Page says that AirShield does not do that but blows around and in between passengers. “You will not feel it blowing on your face as you sit in your seat,” he assures.

“While AirShield reshapes air flow from the vents, it does not alter the cabin temperature or the volume of air supplied beyond that of a traditional air vent. It is also 50% quieter than a traditional vent to help promote passenger rest time,” he adds.

AirShield’s nozzle tips are inspired by industrial ‘air knife’ technology. During the development process, Pexco prototyped more than 20 versions which were 3D printed. “These rapid iterations empowered our engineering team to refine the performance of the technology,” Page says. “They ensured we could achieve the desired impact without modification to the existing cabin airflow system or any recertification to the seating.”

Extra certification costs money, of course. Also, when innovations like Air Shield come along, regulatory authorities sometimes need to create new standards/benchmarks to ensure a system does what it claims. Page reports that Pexco did not set out to rewrite the rulebook. “At every stage of the development process, we ensured AirShield could be certified for the A320 within the existing regulatory framework. Its unique three-piece assembly is lightweight (less than a pound), incredibly durable, and quick and simple to install,” he confirms.

Read Part One Completely IN the comfort zone

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