Gas sensors in environmental monitoring

Metal oxide semiconductor gas sensors in environmental monitoring... 

Fine, G. R, Cavanagh, L. M., Afonja, A. and Binions, R. (2010) Metal Oxide Semi-Condnctor Gas Sensors in Environmental Monitoring. Sensors 10,5468-502. 

Eine GE, Cavanagh LM, Afonja A, Binions R (2010) Metal oxide semiconductor gas sensors in environmental monitoring. Sensors 10 5469-5502... 

The answer lies in microsystem design and fabrication, applied to a relatively simple arrangement of gas sensors (the higher the integration the better). Combined with microelectronics, it is perfectly suited for the mass production of EN modules. Microsystems are usually produced in batches and will meet demand at low cost. Additionally, small size, low energy consumption and long-term stability can be achieved. Of course, not only consumer applications will benefit from the microsystem approach, since the improvements are also relevant to instruments used in industrial applications, medical care or in environmental monitoring. 

The method of activation will be discussed in more detail later. The methods under (ii) are applied especially in automatic measurement, industrial sensors and environmental monitors. Those methods take advantage of e.g. protection of the electrode surface with a semipermeable membrane, or transfer of the species to be measured from contaminated solution to the stream of a carrier gas and so on. The response time of these methods and of automatic titrators and other system under (iii) is rather long and such methods have not been included in this paper. 

The model analytes, which were used to show the sensor performance of the microsystems include carbon monoxide, CO, and methane, CH4. The sensor microsystems were designed for practical applications, such as environmental monitoring, industrial safety applications or household surveillance, which implies that oxygen and water vapors are present under normal operating conditions. In the following, a brief overview of the relevant gas sensor mechanisms focused on nano crystalline tin-oxide thick-film layers will be given. 

For gas-phase sensors, both remarkable selectivity and very low LOD are important. Sensors featuring MIP recognition combined with SAW transduction can meet these requirements. The MIP-PZ chemosensors operating in gases are devised for two main applications, namely for indoor gas inspection and online monitoring of volatile organic compounds. The latter is essential to protect humans from threats of environmental atmospheric pollutants. 

By responding to fumes in cooking areas, car parks, laboratories and similar places, gas sensors can be used to control ventilation fans. In industrial situations the sensor can monitor concentrations of carbon monoxide, ammonia, solvent vapours, hydrocarbon gases, ozone etc., and because of the growing consciousness of environmental pollution and the safety aspects of industrial processes the applications will multiply. 

Sensors Key technical problems involve materials and fabrication methods for both gas and liquid sensors opportunities for utilizing advanced microelectronics and membrane technologies are suggested for applications in environmental, industrial, and clinical systems, including in vivo monitoring of drug delivery systems. 

In a reference work on sensors like the present one, the reader would not like to miss a contribution on applications in environmental control. On the other hand this Held is extremely dependent on the legal aspects in different countries, what makes the inclusion of this topic to our series difflcult. Nevertheless we decided to present at least a brief survey which lists some example information about gas sensors and monitoring systems in environmental control. The description is confined to the situation in North America and Canada. 

In consumer s use, applications of gas sensors related to environmental pollutant gases are carried out mainly for security and amenity. Examples of the applications are, for instance, in the protection from a incomplete burning of combustion apparatus for home use and in the ventilation or condition of indoor atmosphere. A combustion monitoring sensor using SnOj was developed by Tanaka et al.[110] of Figaro Engineering, Japan. The gas water-heater... 

DuPont Biosensor Materials are designed for use in medical monitoring, diagnostics, drug delivery, food and beverage testing, environmental sensors Breathing and protection equipment as well as gas detection and analysis systems... 

Despite the numerous reports, extensive studies of optical O2 sensors are still ongoing to improve performance, reduce cost and size, and develop an O2 sensor for in znvo applications/" The large market for O2 sensors also drives these efforts. The development of field-deployable, compact, low-cost monitors such as those based on OLEDs is therefore highly attractive for gas-phase and DO monitoring in various biological, medical, environmental, and industrial applications. "" ... 

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