CO2-based grey-box model to estimate airflow rate and room occupancy Sebastian Wolf, Maria Justo Alonso, Davide Calì, John Krogstie, Hans Martin Mathisen and Henrik Madsen E3S Web Conf., 111 (2019) 04036 Published online: 13 August 2019 DOI: 10.1051/e3sconf/201911104036