Abstract
We measured an indoor nitrogen dioxide (NO2) concentration in the winter of Sendai by using a sensor element that employed a diazo coupling reaction in a porous glass. The questionnaire survey and measurement results of 95 houses were gathered, and the obtained results were that the average NO2 concentration was 91.6 ppb indicating high indoor air concentration, and the percentage of the data that exceed environmental standard value of NO2 (60 ppb) was 53.7%. Especially, the higher NO2 concentration than the environmental standard and the large percentage of the data that exceed environmental standard has been measured at both the house with an oil stove for heating (150.9 ppb and 81.8%) and the house with an oil fan heater for heating (139.0 ppb and 80.0%). On the other hand, the lower NO2 concentration (59.5 ppb) than environmental standard has been measured at the houses with 24-hour ventilation system. Considering these results, ventilation was an important factor to reduce an indoor NO2 concentration, and the indoor NO2, which was mainly emitted from the combustion-type heater, was extremely high in the case of insufficient ventilation. In Sendai area, it was found that people did not pay attention to ventilation in the winter, because the outside temperature was very low and the ventilation would sometimes lead a decrease in indoor temperature. Therefore, people tend to live in the indoor condition containing the higher NO2 concentration than that in other area of Japan.
