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

Abstract

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.

Prediction of exhaled carbon dioxide concentration using a computer‐simulated person that included alveolar gas exchange

“…On the contrary, the simulation by Wang et al 54 that focused on the CO 2 concentration in a personalized work environment (PWE) showed that the inhaled CO 2 concentration was higher than the volume‐averaged concentration over time, which could be caused by upward flow towards the ceiling. Angelova et al 38–40 also indicated that a region of high CO 2 concentration (1200 ppm and above) was formed in front of the occupant's head when there was downward flow from the ceiling, and they assumed that the inhaled CO 2 concentration differed from the CO 2 concentration measured at both the inlet and outlet of the chamber. Thus, the flow field in the breathing zone and the locations of the outdoor supply inlet and exhaust outlet strongly affect the inhaled CO 2 concentration.…”

“…showed that the inhaled CO 2 concentration was higher than the volume-averaged concentration over time, which could be caused by upward flow towards the ceiling. Angelova et al [38][39][40]…”

“…For this purpose, CSPs incorporating a computational fluid dynamics (CFD) approach were developed because they make it possible to simulate the non-uniform airflow pattern and temperature distribution surrounding the human body indoors, together with CO 2 emissions from breathing. [32][33][34][35][36][37][38][39][40] Bulińska and Buliński 35 analyzed three different breathing models that simulate a micro-environment around the human body, particularly the CO 2 concentration distribution emitted by a sleeping person. They confirmed that complete breathing with inhalation and exhalation should be included in an accurate prediction of contaminant transport from humans.…”

“…Prediction of human CO 2 emissions during continuous breathing with inhalation and exhalation modes requires reliable modeling of human interaction with the ambient indoor environment. For this purpose, CSPs incorporating a computational fluid dynamics (CFD) approach were developed because they make it possible to simulate the non‐uniform airflow pattern and temperature distribution surrounding the human body indoors, together with CO 2 emissions from breathing 32–40 . Bulińska and Buliński 35 analyzed three different breathing models that simulate a micro‐environment around the human body, particularly the CO 2 concentration distribution emitted by a sleeping person.…”

Field Measurements of Bedroom Environment in Winter and Summer on Qinghai-Tibet Plateau

“…9). Angelova et al [12] also found that carbon dioxide emissions from the human body will increase when air temperature in the indoor environment increased. Therefore, the fact that the air temperature in the bedrooms on summer nights was higher than that on winter nights may explain why the CO2 concentration in the bedrooms was higher on summer nights.…”