An empirical model to predict indoor NO2 concentrations

This paper discusses the development of an empirical model to predict indoor NO2 concentration (Cin) from outdoor NO2 concentration (Cout) measured just outside the homes. Concentrations were 48-h time integrated averages. Data from a study carried out on measurement of indoor, outdoor and personal exposure to nitrogen dioxide (NO2) in Mumbai were used in the development of the model. Concentrations were measured over 2-day periods both in winter (February 1996) and summer (April 1996) for 43 respondents. The form of the developed model is Cin = kCout + S/Q, where k, the ventilation factor and S/Q the source term are the model constants. Analysis of variance and regression analysis indicated that type of fuel was the most significant factor influencing indoor concentrations and model constants. Measured indoor concentrations were regressed on outdoor concentrations to evaluate model constants for kerosene and liquefied petroleum gas (LPG), which are the most predominantly used cooking fuels in Indian households. Final models, after evaluating the constants suggested that contribution to indoor NO2 concentration due to indoor sources was higher in kerosene using households whereas in the case of LPG using households, the contribution due to outdoor sources was relatively higher. Results of model validation indicated that the predictive power of the models was good. (author)