The quality of the air we breathe is crucial for our health, well-being, comfort, and cognitive performance. Many contaminants can contribute to the degradation of the quality of air, among others, volatile organic compounds (VOC) emitted from different sources like humans. Humans also exhale carbon dioxide used as a marker of air quality but recently suspected to modify the quality of air as well. Aircraft cabins present indoor environments with distinctive features, where passengers are exposed to a mixture of outside and recirculated air. They are characterized by high occupant density, inability to leave the environment, low relative humidity, need for pressurization, and pollutants whose origin are predominantly passengers and their activities.
The ComAir study aimed to investigate the impact of cabin air quality on passengers’ comfort and well-being when reducing outdoor air intake and changing passenger density; this main objective was additionally extended by studying the effects of exposure to elevated CO2 and pollutants emitted in the cabin. The primary reason for this work was to provide an optimal cabin environment for passengers in terms of comfort and well-being with as low as possible environmental impacts of cabin systems in terms of fuel burn and pollutant emissions.
To meet the project objectives, various proportions of outdoor air (representing bleed air on actual aircraft) in the total air supplied to the cabin and realistic profiles of cabin pressure, noise, temperature, and relative humidity were applied. All tests were performed during simulated flights carried out in the Flight Test Facility low-pressure vessel, which contains the front part of an A310 airplane cabin. Two different experimental designs were used. In the first one, a 2 (occupancy) X 4 (air ventilation regime) factorial design was used. Occupancy denotes the number of people in the aircraft (half vs. fully occupied cabin) and examines the psychological important well-being factor of proxemics. The four ventilation regime levels (with target CO2 concentrations between 1,200 and 4,200 ppm) were: baseline with typical aircraft airflow regimes per person, ASHRAE 161 requirement (standard), ASHRAE 161 half (half of the recommended flow), and a recirculation regime with a target CO2 concentration close to regulatory limit. In the second design, a 2 (VOC) X 2 (CO2) test matrix was used to investigate the disentangled effects of these air quality parameters on well-being (CO2 is used in regulations as a proxy for air quality without knowing the separate impact of VOCs and CO2).
