Investigation of Toilets with Reduced Ventilation Frequencies and Odor Simulation

For a sustainable society, we must consider how to reduce the CO₂ emissions from buildings; however, the ventilation frequency in the toilet (i.e., bathroom or water closet) has not been changed in recent years. Only a few attempts have been made so far to reduce the ventilation frequency in toilets to save energy, despite their further technological developments. In this report, we considered evacuating the odor as soon as possible by providing an exhaust port at the bottom of the wall (hereinafter referred to as baseboard deodorization). We also considered the effect of baseboard deodorization for different toilet (bathroom) sizes. First, we surveyed the relationship between the odor detected by a sensor and a human's olfactory sense and the ventilation volume with the toilet in operation to verify the usefulness of the sensors. Secondly, we analyzed the air environment using computational fluid dynamics (CFD). The results of the measurements and a questionnaire survey showed a certain degree of correlation between the indication of the degree of contamination in the air and the odor intensity. The results of the CFD analysis indicated that large-scale toilets could accumulate air more easily than small toilets; however, in either case, the ammonia concentration could be lowered by using baseboard deodorization. It was also found that the exhaust from baseboard deodorization greatly contributed to reducing the ammonia concentration.