Special miniature ceramic gas sensors to measure oxygen distribution in the plasma wind tunnels originally developed to test heat-shield materials for re-entry spacecraft in extreme conditions is now used in new non-space applications. The small size of the sensor and its fast reaction time have made it possible to develop an improved human breath measurement apparatus, a control system to reduce exhaust gases from heating systems for home and industry, and a handy, easy-to-use portable system to test for hydrogen leakage in industrial installations.