Longitudinal assessment of thermal and perceived air quality acceptability in relation to temperature, humidity, and CO2 exposure in Singapore

Thermal acceptability (TA) and perceived air quality acceptability (PAQA)
are typically analyzed in climate chambers or cross-sectional field
studies. Individual factors, such as expectations and perceived
environment history, may influence the acceptability response.
Longitudinal studies with multi-day design are absent in the literature.
Fifteen Singaporean subjects participated in a 7-day longitudinal
experiment in which they carried a portable sensor that continuously
recorded personal air temperature, relative humidity and carbon
dioxide concentration at 1-min intervals. Instantaneous TA and
PAQA were regularly sampled by survey for each subject. High acceptability
was found at home, restaurants and workplaces, whereas low acceptability
was found for outdoor and transport environments. The participants, from
Singapore's modern tropical environment spent an average of 96% of
their time indoors. Weak associations were reported between
acceptabilities and measured physical parameters taken independently.
Clustering data by location, subject's sleeping ventilation habit,
air-conditioning operation status and the changes in physical parameters
over a designated time period enhanced the understanding of the
acceptability results. In general, acceptability was lower for those who
slept in air-conditioned environments than for those who slept without
air-conditioning. The carbon dioxide mixing ratio was critical for PAQA
predictions but not for TA. The Gaussian process (GP) had a better
predictive power than a multiple linear regression approach. Using GP, we
found that a general predictive model had comparable simulation
performance as for individual predictive models. The longitudinal
experiment has demonstrated effectiveness for TA and PAQA analysis, which
could be beneficial to future studies in personal comfort prediction.