This study took place in 2022, during the corona pandemic, and focuses on cultural houses. For this study, VPO used sensor boxes developed in collaboration with VITO, the indoor@boxes to monitor air quality and ventilation effectiveness. The focus in this research is on measuring CO2 concentration, as this is a good proxi for air quality. Complementary to this, a screening of the ventilation system by a specialised firm was also carried out. The study showed that in most culture houses, in rooms where people stay for long periods of time, values higher than 900 ppm, the health guideline, and indicator for sufficient ventilation are often measured. The combination of CO2 measurements and technical screenings complement each other well and show concretely where improvements are possible and/or needed.