Air quality and relative humidity in commercial aircrafts: an experimental investigation on short-haul domestic flights

Nowadays the achievement of a comfortable environment in aircraft cabins is a factor of paramount importance in air travel business competition; on the other hand, the need of reducing the propulsion fuel cost has driven the airline companies to adopt air handling systems that may reduce the levels of thermal comfort and air quality inside the cabins of commercial airliners. With the aim of contributing to a better knowledge of this matter, this paper reports the results of an experimental study upon the indoor air quality aboard commercial aircrafts for 14 domestic flights less than 1 h and half long. The parameters monitored were temperature, relative humidity and carbon dioxide concentration; the measurements were performed during the whole flight from the take-off to the landing. The relative humidity inside the cabin was also calculated using the rates of outside air and the carbon dioxide as a ventilation tracer; the theoretical results were compared with the measured data. The relationship between relative humidity and carbon dioxide concentration during fights was highlighted in order to define the environmental conditions that may provide acceptable levels of both the air quality and hygrometric comfort to the crew and passengers. The results of calculations confirmed the possibility of improving the hygrometric conditions in aircraft cabins without the need of using humidification systems.