Building occupants' psycho-physiological response to indoor climate and CO₂ concentration changes in office buildings

As people spend more time indoors, it is important to identify the relationship between indoor environmental quality (IEQ) and building occupants’ health. This study aims to analyze building occupants' psycho-physiological response to the indoor climate and CO₂ concentration changes. While the indoor climate and CO₂ concentration change, the study measured verbal scales (Indoor air quality (IAQ) satisfaction, thermal comfort vote (TCV), thermal satisfaction (TS), thermal sensation vote (TSV) and thermal preference (TP)) from 22 healthy subjects as psychological responses and monitored blood pressure (BP) at the seated state as the physiological response. The results are as follows: (i) IAQ satisfaction, TCV and TS had a negative correlation between −0.558 and −0.789 with BP; and (ii) if IAQ satisfaction, TCV and TS were below the neutral level, the systolic BP of some subjects was shown to exceed 140 mmHg, the hypertension warning state. The study is differentiated from previous studies as follows: (i) the verbal scale of the previously-used psychological responses was validated from the perspective of the psychophysiological approach (TCV ≈ TS≠TSV); and (ii) for states with a high CO₂ concentration, even if the operative temperature decreases from warm to neutral, the TCV and TS increase and then BP decreases as opposed to in previous studies. Namely, the unhealthier the IEQ condition is, the more the BP increased regardless of the change in the operative temperature. Through the results of this study, it is possible to implement a healthy indoor environment in both a psychological and physiological approach during the building operation phase.