This thirty years, the public toilet has become improved much. Especially, the improvement consists of the basic function aligning with users’ requirements, the enhancement, and sophistication of the design.

On the other hand, one of the issues is the insufficiency for its security and its maintenance that should be prioritized.

Also, it’ easy to find the gap between city vs. town and male vs. female as well as the disparity in terms of the purpose of buildings, especially in schools vs. commercial facilities, and the consideration for the challenged people.

Even though the facial design improvement has changed the impression of the public toilet in Japan seemingly, deepening and continuity are required so as to pursue sustainable enhancement.

To achieve that, it’s important to cultivate human resources and/or an organization that can supervise those facilities from the design to its maintenance.

In recent years, train station toilets, toilets in public facilities and even home toilets have become more comfortable spaces. However, while permanent toilet spaces are becoming more comfortable, cost and usage conditions cause difficulties for portable toilets such as those used during disasters, construction and events.

This paper explains structural aspects of portable toilets as well as measures against odors.

Portable toilets were installed after the Kumamoto earthquakes last year and are indispensable in times of disaster. Our aim in this paper is to contribute to measures against odors in portable toilets during disasters.

We conducted a research on the toilet situation/malodor in the affected areas at the time of the Kumamoto earthquake. The odor level around outdoor temporary toilets depends on the cleanliness, but in general, it was low or an odor intensity of approximately 2 for flush toilets regardless of toilets being Japanese or Western style. On the other hand, malodor easily occurred with dry toilets when there was no gate valve in the storage tank for human waste. The Japanese type of toilet bowl easily becomes dirty and imposes a burden on cleaning workers, whereas the Western type becomes less dirty but must be defined for gender.

Because toilet preparation at the time of disaster has become increasingly more important, we proposed a method of reducing toilet malodor for affected areas in the future.

Wouldn’t it be nice to use a restful restroom while traveling by vehicles? Years ago, people were happy to find the vehicle with a toilet. Since then, that had become common. Today, people expect to find scentless and cozy restrooms, moreover the restrooms is one of key equipment for setting itinerary. The toilets on vehicles are used in particular to many and unspecified passengers. It is also different from the residential one in view of sewer system. Let’s follow the footprint of this unique toilet improvement history of toilet & sewage treatment system for rolling stock and bus.

The present study examined dimethyl sulfide, a substance with an odor quality that varies at high and low concentrations. The concentration at which the change in odor quality occurred was shown and changes in odor quality and characteristics of odor quality were clarified using this concentration as a base point. The fact that the phenomenon whereby odor quality changes at different concentrations occurs at the odorant receptor level suggests that individual odor thresholds make a contribution. The present study measured individual odor thresholds in ten subjects using the triangle odor bag method to elucidate trends in changes in odor intensity and pleasant/unpleasant evaluation. In addition, sensory evaluations were carried out in 25 subjects to elucidate the concentrations at which changes in odor quality occurred and characteristics of odor quality. The results obtained are shown below.

1) A hundred-fold difference was observed in individual odor thresholds for dimethyl sulfide.

2) Odor intensity showed greater correlation with odor index than odorant concentration, and it was found necessary to use sensory amounts for odor concentration and odor index to examine odor quality.

3) It was found that a change in odor quality was sensed at a concentration eighty times greater than the odor threshold.Vexatiousness and sharpness increased clearly at a concentration a hundred times greater.

The method with self-suction is suggested in the triangle odor bag method which is official method in offensive odor control law. This method has some concerns in terms of accuracy. One of them is the decrease of suction-odor concentration because of leakage from clearance between mask and face of a subject. Therefore, it was compared suction flow rate by using CFD among three width patterns of clearance and three suction patterns based on the measurement. Consequently, it was revealed that the decrease of odor concentration suctioned from odor bag was depended on both the volume of breath, and width of clearance between mask and face. For example, maximum suctioned odor concentration was 67 percent.