This Small Business Technology Transfer (STTR) Phase I project aims to prove the feasibility of developing a solid electrolyte NOX, sensor with a fixed reference and a metal oxide covered sensing electrode for harsh environments. Specifically, the approach will be to use YSZ as solid electrolyte, a coating of microporous zeolite material as fixed reference electrode and metal oxide as auxiliary phase to function as a sensing electrode. There is a continuing need for the development of rugged and reliable sensors capable of making measurements in the harsh environments. The use of sensors results in many benefits, including improved energy efficiency, better quality, lower scrap rate, and reduced emissions. The automotive industry is also challenged to further reduce exhaust emissions from mobile sources. The 1990 Clean Air Act Amendments will also require many power and utility industries to monitor emissions. Emission monitoring sensors include those for CO, NOX, 02, and hydrocarbons. Major advances in these sensors are required in terms of lower cost, selectivity, durability and reliability. <br/> Successful development of the proposed sensor for harsh environments will provide opportunities to increase productivity, decrease scraps, and attain EPA clean air standards in a wide range of industries including foundry, automotive, utility, steel making, waste disposal, and others. A cost-effective, inline sensor and measurement system to monitor NOX in internal combustion engines helps to meet EPA regulations.