Experimentally validated CFD analysis on sampling region determination of average indoor carbon dioxide concentration in occupied space

Measurements of carbon dioxide concentration become a very popular method for determination of the air exchange rate in buildings. In measurement practice applied by many researches only one sensor is used in a single room. This cause that the measured CO2 concentration should represent mean concentration in the room. This cause that the positioning of the CO2 sensors is crucial for such a measurements. This paper attempts to find representative measuring area of mean CO2 concentration in a particular room with one sleeping person using numerical modelling. Different parameters that determine CO2 distribution in the room were analysed. Results show that the geometry of the window opening and internal heat sources have a significant influence on a spatial distribution of CO2. It was found that simplified exhalation compared to a full breathing model of the person is enough precise for accurate CO2 distribution analyses. Representative area of CO2 concentration spreads over the half of the room. CO2 sensors can be positioned in the centre of the room or moved towards the door were the air flows out. Positions which should be avoided during the measurements were in the vicinity of the radiator and window. In case of the sleeping person all the space over the sleeping person must be excluded from the measurements. The distance of the sensor from the wall should be at least 40 cm. The measurements can be successfully made in the centre of the room independently of the room height.