The Humidity Paradox

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 


Humidity in air is an important condition for comfort climate.

  • Humidity is vital for our immune system

  • Humidity is better for our relax and sleep quality

  • Humidity increases our wellbeing and wellness

  • Humidity improves our sense to taste

  • Humidity reduces electrostatic electricity

Wherever people are, humidity is an important factor for the climate to be perceived as pleasant. The body has adapted to the levels found on earth and it feels best if the humidity is between 20 – 60 percent RH. The normal humidity in our homes and workplaces can in winter time be down to 20 – 25 RH. At a humidity of 15 – 20 percent RH, the discomfort from the dry air increases. These are levels that are below what is common on earth. It affects how we feel, although it can be difficult to pinpoint exactly what is wrong. Well-being, taste, smell and the ability to relax and recover are weakened. Difficulty to sleep occurs and the risk of catching a cold increases. At extremely low humidity below 10 percent RH, these effects become more apparent; driven by dehydration of our mucous membranes, skin and eyes. 
Extremely dry air on board 
When we sit in an airplane, the humidity gradually drops in the cabin to reach a level of 5 – 15 percent RH after about three hours. After six hours, the dry air has noticeable negative effects that linger and contribute to jet lag. The lowest is the humidity in the cockpit and the staff’s rest areas where it moves down to zero. In first class where the number of passengers is low, it is often around 5 percent RH and in Business Class 5 – 10 percent RH during long-haul flights. Thus, the air in the plane is drier than anywhere on earth. 
The fresh air lacks moisture 
The fact that the air on board an aircraft becomes extremely dry is due to the fact that the fresh air that is taken in from outside at cruising altitude in principle lacks moisture. The humidity that is supplied naturally comes essentially from the passengers on board. The air circulates in sections in the cabin, which means that the need for humidification is greatest in sections with few passengers. It also means that the air is driest in premium classes where passengers sit sparsely, but where the expectation of comfort is higher and in staff rooms where the dry air is a work environment issue. 




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.