The first step in verifying the design of the rodent Research Animal Holding Facility (RAHF) as a barrier to environmental contaminants was successfully completed at NASA Ames Research Center (ARC) during a 12-day bio-compatibility test. Environmental contaminants considered were solid particulates, microorganisms, ammonia, and odor-producing organics. The 12-day test at ARC was conducted in August 1988, and was designed to verify that the rodent RAHF system would adequately support and maintain animal specimens during normal system operations. Additional objectives of this test were to demonstrate that: 1) typical particulate debris produced by the animal, i.e., feces and food bar crumbs, would be captured by the system; 2) microorganisms would be contained; and 3) the passage of odor-producing organics and ammonia generated by the animals was adequately controlled. In addition, the amount of carbon dioxide exhausted by the RAHF system was to be quantified. Of primary importance during the test was the demonstration that the RAHF would contain particles greater than 150 μm. This was done by analyzing collection plates placed underneath exhaust air ducts and underneath rodent cages during cage maintenance operations, e.g., waste tray and feeder changeouts. No particles larger than 150 μm were found in the collection plates that could be traced to the RAHF. Microbiological testing was performed using standard Rodac plates and a centrifugal air sampler with standard trypticase soy agar strips. No additional organisms were found in the test environment that could be traced to the RAHF. Odor containment was demonstrated to be less than “barely detectable” when samples of RAHF exhaust air were sniffed by a “blind” panel of “qualified” ARC civil service personnel. Ammonia could not be detected in the exhaust air from the RAHF system. Carbon dioxide levels were verified with a standard infrared analyzer to be less than 0.35%.