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.TCCA is composed of two main sorbers containing activated charcoals (AC) and phosphoric acid impregnated AC, a high temperature catalytic oxidizer with two electrical heaters, a gas cooler, and two post sorbers containing alkali impregnated AC.The authors conducted the fundamental tests in order to confirm the TCCA design, and the results shown below are obtained; 1) The phosphoric acid impregnated AC is effective for NH3 adsorption. 2) The palladium-on-alumina catalyst is suitable for CO, CH4, C2H4 conversion at temperature lower than 400°C. 3) The alkali impregnated AC is effective for NO2, SO2 removal and prevents catalyst poisoning from SO2. This paper describes an outline of the fundamental test and design conditions for TCCA.