Indoor air aerosol model: the effect of outdoor air, filtration and ventilation on indoor concentrations

A simple model has been developed to predict the indoor air concentration, indoor surface accumulation and the connection between the outdoor and indo or air concentrations. The model is valid for systems where the chemical re actions are slow or the aerosol size distribution is pretty constant, for e xample for the number concentration of radioactive aerosols (particularly t he total activity) or fungal spores. In the model, several factors such as filtration, ventilation, deposition, re-emission, outdoor concentration and indoor sources are included. When simulating radioactive clouds the model results show that there is always a time period after which the radioactivi ty indoors is higher than outdoors. If the outdoor aerosol particles have a periodic behaviour, also the indoor aerosols behave periodically but smoot her and with some delay. Indoor sources are shown to be able to increase in door concentrations continuously. (C) 1999 Elsevier Science Ltd. All rights reserved.