Low humidity in the aircraft cabin environment and its impact on well-being – Results from a laboratory study

The impact of low humidity in the aircraft cabin environment on the human well-being has been analyzed comparing data from a laboratory subject study. Experiments were performed in a simulated aircraft environment at the Fraunhofer Flight Test Facility (FTF) where subjects were asked to vote their sensation and perception of the environment with respect to humidity as well as their perceived symptoms.The interior of the aircraft was maintained to give subjects a realistic impression of flying while the main environmental parameters have been varied and controlled: air pressure, air and fuselage temperature, relative humidity, background noise, ventilation rate, etc. 40 subjects experienced relative humidities of 10%–40% at a temperature range of 21 °C–25 °C and atmospheric pressures between 753 hPa and ambient conditions. Based on the course of a 7 h long-haul flight the subjects answered questionnaires three times. In this paper the impact of low humidities on both, perceived comfort and symptoms, is analyzed.The percentage of subjects assessing the environment as dry is remarkably high at all levels of relative humidity. However, almost each of the estimated regressions is not significant on a level of 0.05 for all exposition phases. Thus direct relationships between perceived symptoms related to dryness as well as subjective assessment of dryness and relative humidities below 40% could not be drawn. At very low levels of relative humidity around 10% the perception of dryness decreases significantly between 90 min and 240 min after start of exposure.