A CO2-controlled ventilation system

For buildings in which the emissions from people is the main source of pollution, the number of people is the limiting factor for air ventilation. When such buildings are not used at full capacity, the ventilation, and consequently the energy consumption, is unnecessarily high. A great deal of the energy could be saved if the ventilation system could be developed to adjust the air flow to the actual requirements. One possible system would allow the amount of CO2 in the exhaust air to control the ventilation rate. To study if this principle is practicable and economic, a CO2 indicator has been installed in an office building in Helsinki. The mixture of exterior air and recirculated air is adjusted so that the amount of CO2 during working hours is kept on ca 700 ppm (μL/L). The equipment was used during winter 1981-82, and the variation of CO2 and the exterior air flow has been registered. The proportion of CO2 has also been measured locally in order to study occasional variations that may occur. The proportion of other pollutants in the room air has been studied simultaneously with a gas chromatograph. Different types of CO2 indicators were used to study the efficiency of the control system. The successful results indicate that the system can be used in new constructions, as well as in existing buildings.