This model is based on
Buildings.Airflow.Multizone.Validation.ThreeRoomsContam. In
addition, a CO2 source has been added to the left room
in the bottom floor. At initial time, all volumes have zero
CO2 concentration. At t=3600 seconds,
CO2 is added to volWes. As time progresses,
the CO2 is transported to the other rooms, and
eventually its concentration decays.