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Trace contaminant control onboard the International Space Station will be accomplished not only by the Trace Contaminant Control Subassembly but also by other Environmental Control and Life Support System subassemblies. These additional removal routes include absorption by humidity condensate in the Temperature and Humidity Control Condensing Heat Exchanger and adsorption by the Carbon Dioxide Removal Assembly. The Trace Contaminant Injection Test, which was performed at NASA's Marshall Space Flight Center in November and December 1997, investigated the system-level removal of some common spacecraft trace contaminants by these International Space Station systems and subsystem. It is a follow-on to the Integrated Atmosphere Revitalization Test conducted in 1996. An estimate for the magnitude of the assisting role provided by the Carbon Dioxide Removal Assembly and the Condensing Heat Exchanger was obtained.

The application of gas detector tubes to monitor the enclosed environment of a spacecraft was first done in the Skylab 2 mission. There were two contaminants of concern - carbon monoxide and toluene diisocyanate. In the Space Station Freedom program, measurement of trace contaminants in the Node 2 and Lab A atmosphere is required prior to the first entry of the crew. Since Node 2 is isolated from the trace contaminant control system for approximately 100 days during SSF building missions, it is anticipated that the Node 2 atmosphere may contain trace contaminants released over this period and some of these may exceed the acceptable levels. It will also be necessary to use gas detector tubes to measure the oxygen level since the Major Constituent Analyzer will not be powered before ingress.