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Background: A quantitative comfort model will aid in evaluating comfort levels of various target groups before the actual flight of an airplane. However, constructing the model is always a challenge due to the complexity of the phenomenon., Objectives: In this paper, we present quantitative comfort models to predict the (dis)comfort of passengers flying with turboprops based on objective measures., Methods: Ninety-seven participants took part in two experiments conducted during real flights, during which forty of them had environmental and personal factors recorded using (self-developed) measurement tools. The collected data were analyzed to model the relations between objective measures and subjective feelings., Results: Two preliminary models based on gradient boosting regression were developed. The models were able to predict the changes in comfort and discomfort of individual passengers with an accuracy of 0.12±0.01 and 0.21±0.01 regarding normalized comfort and discomfort scores, respectively. Additionally, contributions of different factors were highlighted., Conclusion: The outcomes of the models show that we took a step forward in modeling the human comfort experience using objective measurements. Anthropometry (including age), seat positions, time duration, and row (noise) emerged as leading factors influencing the feeling of (dis)comfort in turboprop planes.

Background: Aircraft cabins are special environments. Passengers sit in close proximity in a space with low pressure that they cannot leave. The cabin is ventilated with a mixture of outside and recirculated air. The volume of outside air impacts the carbon footprint of flying. Higher recirculation air rates could be considered to save energy and divert less kerosene from producing thrust., Objectives: To investigate whether higher recirculation air rates in aircraft cabins negatively affect passengers' health and well-being and if occupancy plays a role in this., Methods: In a 2 (occupancy: full and half-occupied) X 4 (ventilation regime) factorial design with stratified randomization, participants were exposed in an aircraft segment in a low-pressure tube during a 4-h simulated flight. Ventilation regimes consisted of increasing proportions of recirculated air up to a maximum CO 2 concentration of 4200 ppm. Participants rated comfort, health symptoms, and sleepiness multiple times. Heart rate (variability), as stress marker, was measured continuously., Results: 559 persons representative of flight passengers regarding age (M = 42.7, SD = 15.9) and sex (283 men) participated. ANCOVA results showed hardly any effect of both factors on self-reported health symptoms, strong main effects of occupancy on comfort measures, and interaction effects for sleepiness and physiological stress parameters: Participants in the half-occupied cabin hardly reacted to increased recirculation air rates and show overall more favorable responses. Participants in the fully occupied cabin reported higher sleepiness and had stress reactions when the recirculation air rate was high., Discussion: This large-scale RCT shows the importance of occupancy, a previously neglected factor in indoor air research. The proximity of other people seems to increase stress and exacerbate reactions to air quality. Further studies on causal pathways are needed to determine if recirculation air rates can be increased to reduce the carbon footprint of flying without detrimental effects on passengers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: In previous studies, negative associations were found between increased environmental sensitivity and general well-being as well as positive perception of air quality. However, only a few studies with partly inconsistent results examined this relation under exposure. They tried to determine whether people with increased environmental sensitivity react to real environmental conditions with changes in current well-being and perception of air quality., Methods: Pooled data from two single-blinded randomized controlled trials with different exposure levels were analyzed. Participants were exposed to different levels of volatile organic compounds (VOC) and carbon dioxide (CO 2 ) in the front part of a former in-service wide-body airplane inserted in a low-pressure chamber. Three exposure groups were created depending on the VOC/CO 2 levels: low, medium and high. Subjects repeatedly answered questions about their current mental well-being and about perception of air quality and odor intensity. Based on self-reported data the participants were classified into groups with low and higher environmental sensitivity. Data were evaluated using a 2 (environmental sensitivity) x 3 (exposure) ANCOVA with repeated measures., Results: 503 individuals (221 females) participated (mean age: 42.8 ± 14.5 years). Thereof, 166 individuals were assigned to the group with higher environmental sensitivity; they reported poorer psychological well-being regarding vitality (F (1,466) = 16.42, p < .001***, partial η 2  = 0.034) and vigilance (F (1,467) = 7.82, p = .005**, partial η 2  = 0.016) and rated the pleasantness of air quality (F (1,476) = 7.55, p = .006**, partial η 2  = 0.016) and air movement (F (1,474) = 5.11, p = .024*, partial η 2  = 0.011) worse than people in the low sensitivity group. Exposure levels showed no effects. No systematic differences between men and women were found. Increased environmental sensitivity shared common variance with negative affectivity, another person-related variable. Its explanatory power was higher for evaluations of the environment whereas no differences between the concepts in explaining current psychological well-being were found., Conclusions: Even a slightly elevated level of environmental sensitivity led to worse ratings of the environment with no clear relation to the real environment. Consequently, environmental sensitivity should be considered as a confounding factor in environmental exposure studies. The independency from real exposure levels is in line with the results from previous studies showing that the differences in environmental ratings are probably also driven by psychological factors., (Copyright © 2022 Elsevier GmbH. All rights reserved.)

We reviewed 47 documents published 1967-2019 that reported measurements of volatile organic compounds (VOCs) on commercial aircraft. We compared the measurements with the air quality standards and guidelines for aircraft cabins and in some cases buildings. Average levels of VOCs for which limits exist were lower than the permissible levels except for benzene with average concentration at 5.9 ± 5.5 μg/m 3 . Toluene, benzene, ethylbenzene, formaldehyde, acetaldehyde, limonene, nonanal, hexanal, decanal, octanal, acetic acid, acetone, ethanol, butanal, acrolein, isoprene and menthol were the most frequently measured compounds. The concentrations of semi-volatile organic compounds (SVOCs) and other contaminants did not exceed standards and guidelines in buildings except for the average NO 2 concentration at 12 ppb. Although the focus was on VOCs, we also retrieved the data on other parameters characterizing cabin environment. Ozone concentration averaged 38 ppb below the upper limit recommended for aircraft. The outdoor air supply rate ranged from 1.7 to 39.5 L/s per person and averaged 6.0 ± 0.8 L/s/p (median 5.8 L/s/p), higher than the minimum level recommended for commercial aircraft. Carbon dioxide concentration averaged 1315 ± 232 ppm, lower than what is permitted in aircraft and close to what is permitted in buildings. Measured temperatures averaged 23.5 ± 0.8°C and were generally within the ranges recommended for avoiding thermal discomfort. Relative humidity averaged 16% ± 5%, lower than what is recommended in buildings., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)