The Humidity Paradox

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How can air be drier than any place on Earth – causing discomfort and even health issues for people onboard – and at the same time cause fuselage condensation?

This is a paradox. The aviation industry has long tried to curb the side-effects

THE DRY PROBLEM - OUR WELLNESS ONBOARD IN FOCUS

Humidity in air is an important climate condition that has impact on how we feel and function.

Adequate air humidity is vital for our immune system
Air humidity in comfort zone is essential for our relax and sleep quality
Air humidity is important for our wellbeing and wellness
Ground-equvalent air humidity normalizes our sense to taste
Restored air humidity reduces electrostatic electricity

Humidity is an important factor for the climate to be perceived as pleasant. The body has adapted to humidity levels common on earth. Climate feels best if the humidity is between 40 – 60 % RH. But our experience range is down to 20 – 25 % RH which is the normal humidity in our homes and workplaces in winter time. At a humidity of 15 – 20 % RH, the discomfort from the dry air increases. This falls-behind of our comfort level simply because it is below levels on earth. We feel different, although it can be difficult to pinpoint exactly what is wrong. It affects well-being, taste, smell and the ability to relax and recover. We face difficulty to sleep and risk of catching a cold increases. At extremely low humidity below 10 % RH, these effects become more apparent and acute; driven by dehydration of our mucous membranes, skin and eyes.

Extremely dry air on board

Air humidity in an aircraft gradually drops in the cabin to reach a level of 5 – 15 % RH after about three hours. After six hours, the dry air has noticeable negative effects that linger and contribute to jet lag. Humidity is the lowest in the cockpit and crew rest compartments, where air humidity drops to unprecedented low level (below 5 % RH). In first class where the number of passengers is low, it is around 5 % RH and in Business Class it is 5 – 10 % RH.

The fresh air lacks moisture

Air on board an aircraft becomes extremely dry due to the fact that fresh air intake at cruising altitude lacks moisture content. The only source adding humidity is people. The air circulates in sections in the cabin, which means that the need for humidification is greatest in sections with fewest passengers. In other words, air is the driest in premium classes where passengers sit more spacious, in flight deck and in crew rest compartments.

THE WET PROBLEM - OUR CLIMATE IN FOCUS

Excess weight in aircraft cause unwanted and unnecessary increase in fuel consumption and green gas emissions.

Anti-Condensation saves weight
Anti-Condensation reduces fuel consumption and CO2 footprint
Anti-Condensation reduces electronics maintenance
Anti-Condensation prevents rain in the plane
Anti-Condensation reduces build up of mold and fungus

The weight of an aircraft negatively affects fuel consumption, operating costs and carbon dioxide emissions and thus the environment. The weight increases during travel as the air circulating on the inside next to the fuselage shell, which is covered by the cabin’s interior, forms condensation that freezes to ice when the fuselage’s temperature reaches approximately minus 35 degrees Celsius. The amount of condensation that forms during flight is essentially determined by the number of passengers on board and where you fly. During approach and on the ground, this ice melts into water.

Remains in isolation

When the plane has landed, most of the condensed water flows out via drainage channels, so-called passive dehumidification. However, some condensed water remains in the fuselage, mainly in the insulation. If the aircraft is on the ground long enough, this water dries out, but it rarely happens. Instead, more and more water accumulates in the fuselage.

The condensate creates problems

Condensation can increase the weight of a medium-sized passenger plane by up to 200 – 300 kg. Water can also cause corrosion, failure of electronic components and systems and cause unwanted malfunctions. Condensation also destroys the insulation so that it needs to be replaced more often. Calculations show that if the aircraft weight can be reduced by 200 – 300 kg, it could reduce carbon dioxide emissions by between 65 – 100 tonnes per year. Although the aviation industry accounts for a small part of global greenhouse gas emissions, the problem is increasingly accentuated by the growing demands of the outside world for more sustainable air transport.

Optimizing humidity in aircraft