TESTING VALIDATION OF MOBILE AIR QUALITY MONITOR FOR SENSING DILINEATING VOC EMISSIONS

摘要

Volatile Organic Compounds (VOC) are chemical compounds having high vapor pressure and arc volatile in nature at room temperature. There is a limit of VOC content in the air beyond which they can cause respiratory disorders, nausea, loss of coordination and in some cases may lead to lung or kidney damage and many other health hazards. Due to the increase in industrialization and urbanization, there have been VOC emissions in the air to greater scales. This has prompted monitoring of VOCs emissions through innovative sensing technologies which give continuous information of the VOC pollutants in the air. A Metal Oxide Sensor (MOX) is one of the sensors widely used for monitoring VOCs in the air. It consists of a porous layer heated by a filament which undergoes a redox reaction when it comes in contact with a VOC changing the electrical resistance across the circuit in proportion to the concentration of the VOC. This transduction principle gives high sensitivity for monitoring air quality and therefore can be used in continuous monitoring of industrial emissions. An important characteristic while considering this sensor for monitoring air quality is its selectivity which is its ability to discriminate between two compounds. A uRADMonitor A3 sensor consisting of a MOX sensor (Bosch BME680) was used to monitor air quality for determining the air quality index. Initially point source emissions of a gasoline generator (Hyundai 1750VV) were measured by URADMonitor A3 and compared with Horiba MEXA-584L device for validating the measurements. Subsequently two URADMonitor A3 monitors were tested (in identical positions one at a time, and in different positions simultaneously) studying its sensitivity, accuracy, and precision. The electrical resistance values were noted, brought to a common baseline based on each sensor's historical data, and scaled to a normal internal. Linear and non-linear scaling approaches were compared. This normalized scaling approach allowed comparison of two units using the same VOC sensor, but is also intended to work between different types of VOC sensors (e.g. BME680 vs MP503). The goal is to develop an improved method for determination of air quality index at a wide range of concentrations and for a wide range of VOCs.