Advanced Extra-Vehicular Activity systems are necessary for the successful support of the International Space Station beyond 2020, and future human space exploration missions for in-space microgravity EVA, and for planetary surface exploration. The proposed multiparameter monitor responds directly to a NASA need for partial pressure monitoring of carbon dioxide, oxygen and humidity in portable life support systems (PLSS). This device will also have application as a monitor for air quality in the pressurized cabin of crewed spacecraft, improving reliability of closed-loop environmental control systems, and resulting in significant improvements in miniaturization, operational reliability, and sensor life-time. Sensors capable of monitoring trace contaminants in both air and water with functionality in microgravity, low pressure and elevated oxygen environments could be designed using the same sensing technology and optoelectronic unit. There are a large number of potential commercial applications for a combined miniature probe for oxygen, carbon dioxide and humidity, as well as for the individual sensors themselves. Our initial focus will be on market niches where miniaturization, high performance, and operation in mixed gas/aqueous environments are desired. The biotechnology and pharmaceutical industries, which require miniature probes and minimally invasive monitors for accurately determining humidity, oxygen, and/or carbon dioxide for process control, product quality control, and I&R activity, will be target markets. Biomedical monitoring may also be an attractive business opportunity; non-invasive or minimally invasive sensors and miniature probes, for measuring and monitoring PCO2 and PO2, have many potential applications for monitoring tissue oxygen supply and blood perfusion. Finally, and perhaps most importantly, indoor environmental control may provide the largest potential market. Temperature, humidity, CO2 content, and oxygen content, in that order, are by far the most important determinants of comfort in rooms and buildings. A reliable, cost-effective monitor for these parameters, used as part of an advanced heating, ventilation, and air conditioning (HVAC) system could significantly lower energy usage and associated costs.