The influence of ventilation on reactions among indoor pollutants: modelling and experimental observations.

This study examines the influence of ventilation on chemical reactions among indoor pollutants. We have used a one compartment mass balance model to simulate unimolecular and bimolecular reactions occurring indoors. The initial modeling assumes steady-state conditions. However, at low air exchange rates, there may be insufficient time to achieve steady-state. Hence we have also modeled non steady-state scenarios. In the cases examined, the results demonstrate that the concentrations of products generated from reactions among indoor pollutants increase as the ventilation rate decreases. This is true for unimolecular and bimolecuar reactions, regardless of whether the pollutants have indoor or outdoor sources. It is also true even when one of the pollutants has an outdoor concentration that displays large diurnal variations. We have supplemented the modeling studies with a series of experiments conducted in typical commercial offices. The  reaction examined was that between ozone and limonene. The ozone was present as a consequence of outdoor- to-indoor transport while the limonene originated indoors. Results were obtained for low and high ventilation rates. Consistent with the modeling studies, the concentrations of monitored products were much larger at the lower ventilation rates (even though the ozone concentrations were lower). The potential for reactions among indoor pollutants to generate reactive and irritating products is an additional reason to maintain adequate ventilation in indoor environments.