Sensor array for multiple emission gas measurements

The paper presents a low-cost multiple gas sensing device developed for pollution measurements in a kitchen hood which is exposed to grease and dirt. The target application of an ozone control system needs no accurate measurements. Using common electronics for all three sensing elements reduces costs. A single digital processor with a user friendly interface controls the heating power of the sensing elements and reads the measurements. Two sensors can be connected to a single personal computer (PC). The main task of the sensor system is to observe volatile organic compounds (VOC) from cooking emissions and measure the ozone produced in the outlet duct. The sensor gives the total non-specific VOC amount and is not intended for a particular gas. Calibration with ethanol guarantees a representative enough response for most hydrocarbons in cooking emissions. The sensing devices give an indication if more ozone is needed. Practical tests show that the response of the first VOC element is slow but stable, while the second one reacts rapidly (<1 s) to any changes. The combination of the sensing elements gives a very good estimate of the total VOC level. The ozone sensing element also reacts to VOCs, which is a harmful characteristic for the prospective ozone control mechanism. However, with a combination of the VOC and ozone measurements, the errors in the ozone measurement can be reduced. Thus the sensor is like a simple electronic nose (Marco, S. et al., 1998).