HORIBA has developed the INM-700, a low cost, low-maintenance, in situ instrument for simultaneously monitoring NOx and O2concentrations aimed at industrial applications. The INM-700 is based on a novel use of a solid-state zirconium oxide sensor strategy. Using this new configuration, the instrument eliminates the drawbacks such as sample handling and conditioning and time lags associated with more conventional extractive sampling methods. In this paper, we review the development and testing of the HORIBA INM- 700 in preparation for deployment on Selective Catalytic Reduction (SCR) units on coal-fired power plants. We describe the sensor technology developments and modifications implemented to integrate the instrument to the SCR application. We show data to track NOx and O2concentrations at a typical power plant and compare that data to conventional extractive methods. The HORIBA INM-700 data tracks plant history data sets and demonstrates this innovative and affordable approach to industrial process monitoring.