Evaluation of the neutral criterion of indoor air quality for air-conditioned offices in subtropical climates

摘要

Occupant-generated carbon dioxide (CO2) is used as the tracer gas to determine ventilation rate. Although CO2 concentration may not provide a comprehensive indication of indoor air quality (IAQ), it can be a good indicator of the concentration of other human bioeffluents perceived as a nuisance and be used to identify the acceptability of IAQ in a space by its occupants. In this study, the acceptability of IAQ in air-conditioned offices was evaluated by the subjective responses of the office occupants with respect to indoor CO2 concentration. CO2 concentrations at 396 sample locations were measured and subjective responses at those locations were recorded by an electronic questionnaire. Specifically, an occupant's indirect acceptability of the perceived IAQ indicated on a semantic differential evaluation scale was correlated to the occupant's direct acceptability described by a dichotomous scale. The overall acceptability of IAQ from all occupants was then described by a logistic regression model and shown to correlate with indoor CO2 concentration. Practical application: The neutral criterion for IAQ indicated by the CO2 concentrations in some air-conditioned offices in subtropical climates was determined within the range of 620-680 ppm above the outside concentration and would satisfy 70-88% of the office occupants. This study provides a template for applying a statistical frequency analysis and logistic regression model to examine the 'neutral' criteria for IAQ indicated by the indoor CO2 concentrations in air-conditioned offices elsewhere.