Odor problems in toilets with reduced ventilation frequencies

Japan's toilets are generally ventilated 15 times per hour. Despite the development in toilets, the ventilation frequency in toilets has not been changed in recent times. Therefore, there is a possibility that toilets are being excessively ventilated. Reducing the ventilation frequency increases the return air to the heat exchanger and improves the efficiency of the heat exchanger. For an optimal ventilation frequency, we introduce a system that could control the exhaust air using sensors. The primary issue is the odor caused by reducing the ventilation frequency. In this study, we aim to eliminate the odor as quickly as possible by providing an exhaust port at the bottom of the wall (hereinafter referred as “baseboard deodorization”). First, we examined the relationship among the odor sensor, human's olfactory odor identification and ventilation volumes with the toilet in operation to verify the usefulness of the sensors. Next, the air environment was analyzed using computational fluid dynamics (CFD). The results of the measurements and questionnaire survey indicate a correlation between the degree of contamination in the air and the odor intensity. The CFD analyses demonstrated, even after the frequency of ventilation reduced to 5 times per hour, that the ammonia concentration obtained was equivalent to 15 times per hour. To solve the odor problem due to the ventilation reduction, it is important to evacuate air immediately after the odor is generated. Among others, it was observed that a baseboard deodorization system contributes significantly to the reduction in ammonia concentration.