Exhaled Carbon Dioxide as a Physiological Source of Deterioration of Indoor Air Quality in Non-Industrial Environments: Influence of Air Temperature

People are the main reason for the deterioration of indoor air quality (IAQ) due to the continuous physiological metabolism processes in their bodies, including respiration. We present results from an investigation of the influence of indoor air temperature on the concentration of exhaled carbon dioxide (CO2). The investigation was preconditioned by previous findings on the effect of air temperature on human metabolism. However, our literature survey showed a lack of studies on the influence of the indoor air temperature on the exhaled CO2 (or metabolic CO2), which leads to the novelty of our results. Our experiments had two phases: measurement in a university classroom with an installed heating, ventilation, and air-conditioning (HVAC) system during regular classes and measurement in a specially designed small climate chamber, where the time variations of the CO2 concentrations, together with some physiological parameters, were measured. Two indoor air temperatures were set: 23 °C and 27 °C. The results obtained and their respective analyses show the strong effect of the two air temperatures on the CO2 concentration due to exhalation. In the classroom, the CO2 concentration at 27 °C was higher by 6.2% than at 23 °C. In the climate chamber, the CO2 concentration at 27 °C was higher by 9.6% than at 23 °C. Physiological parameters (oxygen saturation pressure, pulse rate, end-tidal CO2, and respiration rate) and their dependence on the air temperature were also measured in the climate chamber, establishing an effect of the temperature on the pulse rate.

Effect of Exposure Time on Thermal Behaviour: A Psychophysiological Approach

This paper presents the findings of a 6-week long, five-participant experiment in a controlled climate chamber. The experiment was designed to understand the effect of time on thermal behaviour, electrodermal activity (EDA) and the adaptive behavior of occupants in response to a thermal non-uniform indoor environment were continuously logged. The results of the 150 h-long longitudinal study suggested a significant difference in tonic EDA levels between “morning” and “afternoon” clusters although the environmental parameters were the same, suggesting a change in the human body’s thermal reception over time. The correlation of the EDA and temperature was greater for the afternoon cluster (r = 0.449, p < 0.001) in relation to the morning cluster (r = 0.332, p < 0.001). These findings showed a strong temporal dependency of the skin conductance level of the EDA to the operative temperature, following the person’s circadian rhythm. Even further, based on the person’s chronotype, the beginning of the “afternoon” cluster was observed to have shifted according to the person’s circadian rhythm. Furthermore, the study is able to show how the body reacts differently under the same PMV values, both within and between subjects; pointing to the lack of temporal parameter in the PMV model.

Laboratory characterisations and intercomparison sounding test of dual thermistor radiosondes for radiation correction

A dual thermistor radiosonde (DTR) comprising two (white and black) sensors with different emissivities was developed to correct the effects of solar radiation on temperature sensors based on in-situ radiation measurements. Herein, the DTR performance is characterised in terms of the uncertainty via a series of ground-based facilities and an intercomparison sounding test. The DTR characterisation procedure using laboratory facilities is as follows: individually calibrate the temperature of the thermistors in a climate chamber; test the effect of temperature on the resistance reading using radiosonde boards in the climate chamber; individually perform radiation tests on thermistors; and perform parameterisation of the radiation measurement and correction formulas using an upper air simulator with varying temperature, pressure and ventilation speed. These results are combined and applied to the DTR sounding test conducted in July, 2021. Thereafter, the effective irradiance is measured using the temperature difference between the white and black sensors of the DTR. The measured irradiance is then used for the radiation correction of the DTR white sensor. The radiation-corrected temperature of the DTR is mostly consistent with that of a commercial radiosonde (Vaisala, RS41) within the expanded uncertainty (~0.35 ℃) of the DTR at the coverage factor k = 2. Furthermore, the components contributing to the uncertainty of the radiation measurement and correction are analysed. The DTR methodology can improve the accuracy of temperature measurement in the upper air within the framework of the traceability to the International System of Units.

Thermal comfort environment for migrants: a long-term follow-up climate chamber experiment

Migration between different climate regions may change people’s thermal experience and their thermal adaptation. However, few studies have explored the thermal adaptation process and the suitable indoor thermal environment of migrants. In this study, we conducted a long-term tracking comparative experiment on thermal adaptation of migrants moving from severe cold (SC) regions, hot summer and cold winter (HSCW) regions, and hot summer and warm winter (HSWW) regions to cold region of China. A two-year climate chamber experiment was conducted to follow migrants’ progressive thermal adaptation, such as different weeks, months and seasons after they migrated. The results show that the thermal sensation of migrants was significantly associated with their origin, the time after migration and air temperature. In addition, with the increase time after migration, the thermal sensitivity of HSCW and SC migrants showed a significant upward and downward trend, respectively. Two years after migration, the thermal comfort limits of migrants from SC, HSWW and HSCW were almost identical at 23.5-27.8°C, 23.8-27.8°C, and 23.5-27.6°C. The results provides insight to the progression of thermal adaptation and helpful to guide the design of indoor climate for immigrants with different thermal experiences.

Will correlated colour temperature affect peoples’ thermal sensation outside the laboratory?

Earlier studies have shown that low Correlated Color Temperature of lighting (CCT) may induce a warmer thermal sensation than high CCTs at the same ambient temperature. The current study investigated if the association between CCT and thermal sensation would persist when subjects worked on computers, were exposed for longer duration and when the study population included older subjects whose vision may have changed with age. The study was carried out in a climate chamber with controllable LED lighting and where CCT could be gradually changed. Generally, the association between CCT and thermal sensation was weak and not significant. However, at 22°C and short-term exposure, the results indicated that high CCT caused a cooler thermal sensation. This association disappeared with more prolonged exposure duration and when subjects worked on a computer. Comparison of responses to lighting exposure of the two groups of subjects with mean ages of 24 years and 44 years showed no difference in their perceived thermal sensation when the CCT was changed. However, the older group of subjects could not distinguish differences in CCTs above 4000 K. The findings suggest that the magnitude of the effect of lighting on thermal perception is modest and only visible under exceptional and tightly controlled conditions that do not mirror actual buildings.

Experimental analysis of the thermal comfort provided by an electrical heater and a heat pump

After considering heating sector, one realises that there is no clear and consensual way to quantify or qualify the thermal comfort of the different technologies available to satisfy the heating demand of a home. This contribution tries to call attention to this by means of an experimental study of the thermal comfort provided by two very different technologies, an electrical heater and a heat pump. To do so, a test matrix is developed by considering [2]. Some experiments are carried out in a climate chamber constructed following [1]. The variables registered are used to determine the comfort variables defined in [3] for each technology. After both technologies are compared and some conclusions are drawn.

Validation of a coupled <i>δ</i>²H_{<i>n</i>-alkane}–<i>δ</i>¹⁸O_sugar paleohygrometer approach based on a climate chamber experiment

The hydrogen isotope composition of leaf-wax-derived biomarkers, e.g., long-chain n-alkanes (δ2Hn-alkane), is widely applied in paleoclimate. However, a direct reconstruction of the isotope composition of source water based on δ2Hn-alkane alone is challenging due to the enrichment of heavy isotopes during evaporation. The coupling of δ2Hn-alkane with δ18O of hemicellulose-derived sugars (δ18Osugar) has the potential to disentangle this limitation and additionally to allow relative humidity reconstructions. Here, we present δ2Hn-alkane as well as δ18Osugar results obtained from leaves of Eucalyptus globulus, Vicia faba, and Brassica oleracea, which grew under controlled conditions. We addressed the questions of (i) whether δ2Hn-alkane and δ18Osugar values allow reconstructions of leaf water isotope composition, (ii) how accurately the reconstructed leaf water isotope composition enables relative humidity (RH) reconstruction, and (iii) whether the coupling of δ2Hn-alkane and δ18Osugar enables a robust source water calculation. For all investigated species, the n-alkane n-C29 was most abundant and therefore used for compound-specific δ2H measurements. For Vicia faba, additionally the δ2H values of n-C31 could be evaluated robustly. Regarding hemicellulose-derived monosaccharides, arabinose and xylose were most abundant, and their δ18O values were therefore used to calculate weighted mean leaf δ18Osugar values. Both δ2Hn-alkane and δ18Osugar yielded significant correlations with δ2Hleaf water and δ18Oleaf water, respectively (r2=0.45 and 0.85, respectively; p<0.001, n=24). Mean fractionation factors between biomarkers and leaf water were found to be −156 ‰ (ranging from −133 ‰ to −192 ‰) for εn-alkane/leaf water and +27.3 ‰ (ranging from +23.0 ‰ to 32.3 ‰) for εsugar/leaf water, respectively. Modeled RHair values from a Craig–Gordon model using measured Tair, δ2Hleaf water and δ18Oleaf water as input correlate highly significantly with modeled RHair values (R2=0.84, p<0.001, RMSE = 6 %). When coupling δ2Hn-alkane and δ18Osugar values, the correlation of modeled RHair values with measured RHair values is weaker but still highly significant, with R2=0.54 (p<0.001, RMSE = 10 %). Finally, the reconstructed source water isotope composition (δ2Hs and δ18Os) as calculated from our coupled approach matches the source water in the climate chamber experiment (δ2Htank water and δ18Otank water). This highlights the great potential of the coupled δ2Hn-alkane–δ18Osugar paleohygrometer approach for paleoclimate and relative humidity reconstructions.