The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project lies in the opportunity to provide accurate, real time information to motivate patients to manage their disease; drive early, evidenced-based interventions; and prevent unnecessary physician visits and hospital stays. This non-invasive device, a breathalyzer, will measure the level of ammonia in exhaled breath. High ammonia levels are associated with conditions such as advanced liver disease, urea cycle disorders (UCD), or adverse reactions to medication. It has serious consequences: disorientation, organ/brain damage, coma and even death, making it important to take steps to quickly reduce systemic ammonia and, if the cause is unknown, trigger further diagnostic activities. Currently, ammonia levels are determined through blood testing, which is invasive, takes time, requires a lab/hospital visit, and is prone to errors. There are no tools available to accurately measure ammonia, real time. The device will enable patients and families to take control and make better decisions: what to eat, when not to drive, when to go to the hospital, among other things. This can improve productivity, enhance quality of life for patients and their families, avoid unnecessary healthcare expenditures, and save lives. The proposed project seeks to develop a breathalyzer prototype to detect ammonia in exhaled breath. The device is expected to provide clinically-accurate, real time information to patients and clinicians. Ammonia occurs naturally as a by-product of protein metabolism but, at elevated levels, it is indicative of disease and can have very serious consequences. Contemporary research has identified roughly 250 common volatile organic compounds in exhaled breath, many associated with specific diseases. Small concentration differences can detect whether someone is healthy or ill. This requires highly sensitive, selective and durable sensors that can perform in high humidity. The core platform is a Reactive Spray Deposition technology, a proprietary sensor manufacturing technology that creates a porous nanostructure metal oxides grains layer, and is able to provide results with a fast response time at a low cost. This results from the ability to easily and inexpensively produce different morphologies of materials from the vapor phase in the open atmosphere in a one-step process. The end-product of this project will be a prototype utilizing a single sensor for detection of NH3. It will include a novel breath delivery system and associated signal processing algorithms for quantification of the gas concentration in breath, based on the sensor response.