Checking of ventilation rates by CO2 monitoring.

The present paper presents results from measurements of outdoor airflow rates and air change rates carried out simultaneously with measurements of the indoor concentration of carbon dioxide (CO2 ) . The measurements were made both under controlled laboratory conditions and in the field. The field experiments were performed in a conference room, an assembly hall and an office room, and the laboratory investigation was carried out in a 19 m³ test chamber. CO2 measurements can be successfully used to estimate the outdoor airflow rate in occupied rooms, but it is vital that the methodology takes into consideration a number of possible sources of errors. For example, it can not be presupposed that steady-state conditions prevail. However, inaccuracies due to non steady-state conditions may be reduced by a thorough analysis of the measurement results. Furthermore, it is demonstrated how the air change rate can be determined using a method based on analysis of the CO2- concentration decay in a room.