Household indoor concentration levels of nitrogen dioxide (NO₂) and ozone (O₃) in Eskişehir, Türkiye

The concentrations of nitrogen dioxide (NO₂) and ozone (O₃) were determined at five indoor environments (corridor, living area, bedroom, kitchen, bathroom) of two homes located in different regions of Eskişehir, Türkiye. Home 1 is located in the city center and urban residential area while Home 2 is located in a suburban area. In order to determine the indoor and outdoor (I/O) ratios of the pollutants, outdoor sampling was also carried out simultaneously with indoor sampling. Sampling studies were performed in one-day periods in four seasons by using passive sampling method. The indoor NO₂ concentrations varied between 8.80 - 124.18 µg/m³ while O₃ concentrations varied between 3.69 – 169.00 µg/m³. The highest NO₂ concentrations were determined in the kitchens both in two homes. This can be due to the intensive cooking activities carried out in the kitchens. The variation of O₃ concentrations in the measured indoor environments varied in homes. When the outdoor concentrations were examined, it was seen that NO₂ concentrations were higher in Home 1 and O₃ concentrations were higher in Home 2 in all seasons. This result is related to the location of the homes. The I/O ratios for NO₂ were generally > 1 for the kitchens. Also, all I/O ratios for NO₂ in Home 2 were found > 1 in autumn season. The I/O ratios for O₃ were found < 1 in both homes, except for Home 1, in the autumn season. Seasonal variations of the pollutant concentration levels were also observed for indoor environments. Indoor NO₂ concentrations, especially in Home 1, and O₃ concentrations, especially in Home 2, were higher in spring and summer compared to other seasons. The reason for this is thought to be more active natural ventilation due to the warming of the weather in these seasons.