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The Closed Ecology Experiment Facilities (CEEF), designed to simulate material circulation, is an artificial closed agricultural ecosystem with plants, humans, and animals. The drying toilet system “DRI-LET®” had been installed in the habitation module as a human waste processor for material circulation by carbonizing. Carbonizing of human waste has advantages in life support systems because it can minimize the total volume and weight of human waste. However, this toilet system releases many gases during processing. In particular, NO2 concentration in the habitation module increased up to 4 ppm when one person used the toilet system. In this paper, we report NO and NO2 behavior in the habitation module during experiments and a method to reduce their concentrations by using NO and NO2 adsorbent.

In the closed environments such as manned space station, it is necessary to remove contaminant gas to keep a suitable environment. Removal of gaseous contaminants generated from crew, animals, and plants is important function to keep the environment below the allowable level in the Closed Ecology Experiment Facilities (abbreviated as CEEF). CEEF consist of three modules for habitat, animal and plant, the supporting facilities for each module and a plant cultivation facility. CEEF are scheduled to be constructed from 1994 in Aomori Prefecture, northern part of Japan. For designing Trace Contaminant Control Assembly (TCCA) for CEEF, the following six (6) trace contaminants have been selected as major contaminant gas in CEEF; Ammonia (NH3) Methane (CH4) Ethylene (C2H4) Carbon Monoxide (CO) Nitrogen Dioxide (NO2) Sulfur Dioxide (SO2) Ethylene is well-known as an aggressive contaminant to plant growth and maturity.