The impact of real-time carbon dioxide awareness on occupant behavior and ventilation rates in student dwellings.

• We report on air quality intervention in 60 student dwellings in Denmark and Switzerland. • Visual air quality feedback significantly altered user behavior in half of the dwellings. • Air quality awareness led to reduced median CO 2 levels in 77% of bedrooms. • Air quality awareness doubled the ventilation rates in 70% of dwellings. • Display-integrated CO 2 monitoring is an effective air quality intervention in student dwellings. Although existing standards typically prescribe fixed ventilation rates, a large portion of the building stock lacks mechanical ventilation systems. Such buildings obtain outdoor air through unintentional infiltration, open windows, and the operation of exhaust fans, which are mainly dependent on user awareness and behavior. This study investigates whether the presence of a simple CO 2 meter display can alter user behavior and improve indoor air quality (IAQ) in dwellings. We conducted a two-week monitoring of CO 2 concentration, air temperature, and relative humidity in 60 student dwellings (bedrooms and living rooms) in Denmark and Switzerland. During the first week, the CO 2 display was concealed, and occupants adhered to their usual routines. In the second week, occupants used the display's visual feedback to enhance IAQ when necessary. Results revealed that over 95% of dwellings witnessed a reduction in median CO 2 levels during the second week, both overall and in individual rooms. Furthermore, a descriptive analysis of CO 2 concentration step changes exceeding the thresholds of "normal variation" showed an increase in the number of negative step changes, indicating a shift in user behavior. These findings underscore the efficacy ofa display interface providing information on the indoor environment in triggering behavior changes and improving IAQ in dwellings. [ABSTRACT FROM AUTHOR]