Modelling of indoor pollutant concentrations that varies in time can be a useful tool forestimation of the strength of internal sources and sinks. Usually the modelling has beencarried out using one zone, i.e. with the assumption that the air is well mixed [1,2,3]. Thepresent paper demonstrates that the methodology may be modified to fit multizone situations.By studying the decay of a tracer gas, a correct model can be obtained for a specific volume ina building.
After a literature review about zonal models, we have developed a simplified approach to simulate buoyancy-driven flow in rooms. With two different simple models we have computed the Annex-20 test case d using the procedure prescribed by Lemaire (Annex 20 report, R.I. 1.15). The two simplified methods employ a two-zone and five-zone model. The simulation results of test case d are submitted for comparison with experimental data of heat fluxes and air temperature profiles. The two-zone and five-zone models are also compared with each other.