38


Air Monitoring


crops yield by 5%. Consequently, the costs of ozone pollution are of major concern for national health services, farmers, foresters and others.


Industrial applications of ozone


Ozone has many industrial and consumer applications but cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site. The largest use of ozone is in the preparation of pharmaceuticals, synthetic lubricants, as well as many other commercially useful organic compounds.


In air


Devices generating high levels of ozone are used to sanitise and deodorise uninhabited buildings, rooms, ductwork, woodsheds, and boats and other vehicles. Ozone is also used in fruit ripening process by ethylene control. Ethylene created by plants increases the intracellular levels of certain enzymes in fruit and fresh-cut products responsible of ripening. Ripening process of fruits and flowers is delayed in an ozonated atmosphere because ethylene is oxidised by ozone and is transformed in carbon dioxide and water. Using sensor-controlled ozone generators allows maintaining ozone level between 2 and 7 ppm. At temperature below 5°C and with such ozone level, it is possible to dramatically slow down ethylene production and prevent over-ripening and problems associated with aging.


In water


AUTHOR DETAILS Nicolas Moser


e2v microsensors S.A.


Nicolas Moser is Application Engineer and Technical


Specialist in gas sensing at e2v-


microsensors. He is holder of a postgraduate in measurement & test equipment and industrial imaging.


Courtils 1 CH-2035 Corcelles SWITZERLAND Tel: ++41(0)32 732 16 70 Fax: ++41(0)32 731 01 24 Email:


nmoser@microchemical.com Web: www.e2v.com


Gaseous ozone, created by ultraviolet light or by corona discharge and fed by-oxygen concentrator, is injected into the water to disinfect for bacteria, virus and other microorganisms. Once ozone has entered the cell, it oxidises all essential components (enzymes, proteins, DNA, RNA). When the cellular membrane is damaged during this process, the cell falls apart. Once ozone has decayed, it leaves no taste or odor in drinking water. Ozone is also used for other purposes such as to allow lower temperature wash water and to minimise residuals in wash processes ranging from laundry to semiconductors.


long enough, ozone by itself is ineffective at preventing cross- contamination among bathers and must be used in conjunction with these halogens. Ozonated water is used also to launder clothes and to sanitize food, drinking water, and surfaces in the home. It can also be used to remove pesticide residues from fruits and vegetables.


For any application (bottled water plant, food treatment systems, sterilizing systems, wastewater treatment, aquaculture) ozone should be efficiently dissolved into the water, and the dissolved ozone should be measured at various points in the process to ensure that the process stay efficient over time. Gaseous injected ozone is monitored by ozone in water analyser. Ambient ozone is also controlled by ozone sensors, these ones check if the ozone destructor works sufficiently. Smart sensor located in the right location can communicate the level of ozone generated and control the ozone generator system. This allows keeping a stable process, optimising the power consumption and saving energy.


Conclusions


Ozone monitoring is used in environmental monitoring for health and crop yield concerns and also in industrial processing. A significant proportion of the urban population still lives in cities where certain air quality limits (set for the protection of human health) are exceeded. The need to reduce exposure to air pollution remains an important issue. Moreover, without emissions restrictions, growing fuel combustion worldwide will push global average ozone up 50 percent by 2100. The population has to be warned and informed of the dangers of air pollution, especially on hot summer days. Improvements in monitoring and availability of information on air pollution are another of the success stories of recent years. In some urban area, when someone is planning a day in a city, this person can log onto web service or cellular network providing a host of regular information on air quality. Using maps, one can scan readings and forecasts for ozone. The data are relayed to the web from monitoring stations around this city. Using SMS service, the mobile network operator can regularly inform customers on air quality around his location. If the level is moderate, high or very high, people will consider following cautionary guidelines. The warning advises people with breathing problems to take precautions such as avoiding strenuous exercise while the ozone levels remain high.


In the earliest days of ozone research, cracks in rubber served as the indicators used by scientists to determine atmospheric concentrations of ozone. There is now a wide range of products suitable for the various ozone monitoring applications. From cost effective solutions with micro systems based on MEMS gas sensors using Metal Oxide Semiconductors (MOS), passive tubes, UV analyser or LIDAR (Light Detection and Ranging).


Micro-sensors stand-alone solution developed to offer an alternative to market at a lower cost than UV-analyser and with much higher accuracy and information content than passive tubes represents a promising technology in several fields of application like the detection of ozone peaks, meshing, micro-meteorology, evaluation of exposure of population.


OZ-47: Smart ozone sensor board


Ozone is used in swimming pool and hot tubs to kill bacteria and to reduce the amount of chlorine or bromine required by reactivating them to their free state. Since dissolved ozone does not remain in the water


For new applications and development it is always best to talk directly with the gas monitoring device manufacturer. The application engineers can offer relevant expertise and guide you through your development or buying process.


OMC-3: Ozone Monitoring Cell


Automatic isokinetik sampler ISOSTACK G4


Main characteristics:


- High precision pressure and temperature sensors - 5 points correction curve programmable for each parameters - Wide pumps range from 3 to 9 m3/h - Built-in probe and filter heating - USB stored data download


- Long maintenance interval on vacuum pump - Fast regulation of isokinetic condition at any flow condition - Utility software


- Sampling activities for: isokinetic, constant flow, impactors We control the ambient air quality since 1974 www.tecora.it


Via Volta 22 - 20094 Corsico (Milan) - Italy Tel. +39 02.4505501 Fax +39 02.48601811 tcrtec@tecora.it


New Innovative Zero Air Generator for Air Quality Monitoring Systems


Casella Monitor introduces a time and cost-saving original product to its range of ambient monitoring equipment.


Its new, cartridge-based, ZeroGen zero air generator removes the need for zero calibration gas cylinders when performing calibration checks on ambient air gas analyser systems.


The cartridges are designed to be easily replaced each year, saving considerable time and expense compared to the use of traditional zero calibration cylinders.


Gary Noakes, Product Manager at Casella Monitor, said: Operators of Air Quality Monitoring stations will benefit from reduced operating costs, and achieve a higher accuracy of data with the installation of the ZeroGen.


The Zerogen scrubs the incoming ambient air and produces a purer true zero gas for calibration without all the complications and mechanics of transporting and installing zero calibration gas cylinders.


info@tecora.it Reader Reply Card no 178 Reader Reply Card no 101 IET May/June 2010


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68