Compact, Low-Cost, Long Optical Path, Mutiple Gas NDIR Sensor

There is a need for affordable atmospheric and industrial monitoring and controlling systems that can reliably detect and quantify volatile organic compound (VOC) pollution sources within the U.S. Environmental Protection Agency range of regulating standards. These sensors must measure VOC concentration in the range of 1 to 50 ppm to a high degree of accuracy and with a very short response time. Although there are several sensor architectures available that may meet some of these demands, Ion Optics, Inc., submits that only a nondispersive infrared (NDIR) based detection scheme will meet all of them. The goal of this Phase I research project is to develop an innovative NDIR system based on a highly compact, folded-path optical design. The specially designed optics will enable the use of incoherent broadband sources and sustain high throughput efficiencies over sufficiently long optical path lengths, thus enabling detection limits approaching 1 ppm of hydrocarbon (HC) based VOCs. The proposed system is compact, robust, and readily deployable in the most demanding atmospheric and industrial environments. A prototype system has demonstrated low ppm CO sensitivity in high-pressure, high-humidity, and percent-level background CO2 diesel exhaust streams. Ion Optics, Inc., proposes further innovative design modifications of the sensor for accurate detection of any VOC as well as determination of the total VOC mass flow. This will be accomplished by strategic selection of band pass filters selected to coincide with the strongest HC absorption peak (common to all VOCs) and one or two satellite peaks unique to the selected constituents. By calibrating the sensor response to known concentrations of high purity gas, the signal processing algorithms then may be adapted for identification and mass analyses of the selected constituents. The estimated cost for this instrument when manufactured in quantity would be less than $100.