Current aerosol irritant assays trap animals in noxious atmospheres and put a lot of stress on them. For this reason, the Minimal Animal Stress Irritant Assay Chamber (MASIAC) was developed based on the principle of avoidance, and evaluated. The MASIAC reproducibly detected citric acid with more sensitivity than conventionally used assays. With a group of mice tested simultaneously, the responses were not significantly affected by the presence of other mice. In addition, following multiple exposures to citric acid, the mice either sensitized to the irritant, or learned to avoid it. This suggests a number of areas where the MASIAC could be applied, including behavioral and asthma research. If this new method turns out to be as good as currently used assays, it could provide investigators with an alternative, more humane method of evaluating pulmonary irritants.