Beyond the NASA application, there are significant opportunities for an innovative humidity sensor in the commercial sector including: food processing, agricultural and pharmaceutical industries, indoor air quality control, heating/air conditioning systems, and industrial process control. Humidity and temperature transmitters are being introduced for climate control in luxury cars. Moisture control during construction plays a key role in preventing microbe growth and monitoring concrete drying. Moisture sensors are also used for control of the basement and crawl space ventilation in residential buildings, especially in areas prone to flooding and with soil expansion problems. Many high temperature baking and drying processes require water vapor control. All of these applications share a common problem, the need for reliable and robust humidity sensors, which can resist environmental contamination and wetting. Significant advancements have been made in technology to implement Significant advancements have been made in technology to implement regenerative, closed loop environmental control and life support systems (ECLSS). Humidity is a critical variable for monitoring and control in ECLSS because it can affect the operation and efficiency of a number of key subsystems. Currently, humidity is monitored on the International Space Station primarily in the crew cabin using a mass spectrometer, which is complex, costly, and not amenable to in-situ process control. However, a network of reliable and ultra-compact humidity microsensors, developed in this program and distributed at specific locations within the ECLSS, would allow for real-time process control over the critical O2, H2, and CO2 gas streams used in ECLSS.