The impacts of outdoor concentration of nitrogen dioxide on its indoor level

Abstract

This study examined the infiltration of oxides of nitrogen (NOx) from outdoor into the indoor environments in the commercial areas of Osogbo, Nigeria. Outdoor NOx concentrations were monitored at four different locations with a high volume of commercial and vehicular activities using Toxirae II NOx monitor. A control sampling point was also set at another location with no commercial and vehicular activities. The indoor concentrations at each location were simulated using IAQX 1.0f simulation tool of the US EPA. The mean measured outdoor NOx concentration over the entire commercial area ranged between 0.14 and 0.58 ppm with an average of 0.351 ppm but at the control point it ranged between 0.0 and 0.2 ppm with an average of 0.027 ppm. A simulation of the indoor concentration revealed an unhealthy indoor air quality. The stabilized indoor concentrations at commercial areas ranged between 0.054 and 0.169 ppm but it was 0.00917 ppm at the control point. The study establishes that emissions associated commercial activities may contribute significantly to indoor air quality degradation in an unplanned area thus calls for appropriate regulatory measures to protect public health.