Placement and utilization of CO2 measurements in the ventilation and occupancy assessments

Abstract

Continuous carbon dioxide measurements have typically been used to adjust the demand-based ventilation. With the global COVID-19 pandemic, the use of measurements to ensure the functionality of ventilation and to assess the utilization rate of the space has increased in importance due to the significant impact of air exchange on the spread of the disease via aerosols. The work aimed to examine the spread of carbon dioxide in the room and how the location of the sensors and space users affects the measurement result. In our study, six carbon dioxide sensors were placed in the room that serves as a teaching restaurant. Five sensors were placed in the space itself and one sensor in the exhaust valve. Two meals were arranged, each attended by 10 people. The location of the persons in the space was also monitored. Based on the measurements, it was assessed how the air distribution of the space and the location of the users affected the measurement result of carbon dioxide. It was found that the carbon dioxide content measured close to diners differed from the result measured in the exhaust duct. Because the air in the exhaust duct is mixed with more fresh supply air than in the vicinity of the dining table, it can be thought that the concentration measured in the exhaust duct can indicate better the air variability of the whole space. On the other hand, sensors located closer to the seating area are potentially better positioned from the demand-based ventilation point of view. In the future, it will be necessary to study the issue in more detail for different types of premises and to examine the application of ventilation and space utilization assessment to real-time monitoring of the risk of airborne infectious diseases, for example.