Extravehicular activity (EVA) for maintenance purposes exposes the astronaut and associated gear to toxic substances such as hydrazine and ammonia. Adsorption of these compounds on surfaces of the EVA gear allows them to be carried into the S.S, Freedom atmosphere when the astronaut clears the airlock. A quadrupole based mass analyzer system is proposed for use as an External Contaminant Monitor (ECM) to monitor these and other compounds. The unit occupies approximately 0.5 cu ft, requires 16 W of power, and weighs 22 pounds. It can pinpoint contamination sources with high sensitivity, identifying both known target and also unknown, “stranger,” compounds.