Applying the electronic nose in the environment : requirements for the sensors

Conference (2002, September)

For few years, the department "Environmental monitoring" at FUL applies the principle of the electronic nose equipped with tin oxide sensors to recognise and to monitor real life malodours in the ... [more ▼]

For few years, the department "Environmental monitoring" at FUL applies the principle of the electronic nose equipped with tin oxide sensors to recognise and to monitor real life malodours in the environment and directly in the field. <br />For such emissions, the gas mixtures are very complex and only their odour should be of interest, and not their chemical composition. <br />Moreover, working in the field implies various constraints. <br />The obstacles of the monitoring of real life environmental odours with an electronic nose can be classified into three main areas : the final goal of the study (measuring an odorous annoyance), the analysed sample itself (influenced by the evolution of the process and of ambient parameters) and the operating conditions (necessity to transport the reference gas and the batteries in the field, influence of air humidity). <br />The paper describes the approach of FUL to the problem with various tests conducted in the field with home-made electronic noses based on tin oxide sensors and with very simple configurations. The conclusions, which can be extrapolated to any other sensor types, are promising, but the sensor performances (sensibility, reproducibility, electrical consumption, drift, etc.) should still be improved before reaching the final goal. [less ▲]

Détection des moisissures de l'habitat par un nez électronique

in actes des conférences Eurodeur-airodeur (2002, June 25)

Assessment of odour annoyance by e-nose in the field : some results

in Sbeverglieri, G. (Ed.) 1st Nose II Short Course, lectures and poster abstracts (2002)

Solvent detection in indoor air with a sensor array

in Proceedings of the 8th conference Eurodeur (2001, June)

Air composition in dwellings and public buildings is studied by means of gas chromatography and a sensor micro array 01D28 (MICROSENS, Swiss). Only benzene and its alkyl-derivatives are quantified. The ... [more ▼]

Air composition in dwellings and public buildings is studied by means of gas chromatography and a sensor micro array 01D28 (MICROSENS, Swiss). Only benzene and its alkyl-derivatives are quantified. The micro array 01D28 is composed of six metal oxide gas sensors (SnO2 doped by Pd) equipped with standard or inter-digited electrodes. Isothermal working mode (500oC for all sensors) is applied. Conductivities after 10 minutes of signal acquisition in the studied air are considered as characterizing its chemical composition. Discriminant Function Analysis (DFA) and different linear regression techniques (Inverse Least Squares, Principal Components Regression and Partial Least Squares) are applied to find a relation between the sensors signals and the indoor air composition as determined by the gas chromatography. The presented results suggest that the monitoring of aromatics substances in the indoor air by means of a micro-array of metal oxide gas sensors is possible. The array distinguishes polluted and non-polluted air and it can even evaluate the concentration of the benzene and the toluene. [less ▲]

Chemometrics methods for the identification and the monitoring of an odour in the environement with an electronic nose

in Ramirez-Silva, Maria Theresa (Ed.) Sensors and chemometrics (2001)

The purpose of the paper is to briefly review some researches regarding the adaptation of the electronic nose principle to recognise some malodour sources in the environment, if possible directly in the ... [more ▼]

The purpose of the paper is to briefly review some researches regarding the adaptation of the electronic nose principle to recognise some malodour sources in the environment, if possible directly in the field, and to monitor the odour intensity continuously. Research aims at improving the portability and the user-friendliness of the instrument, together with testing what kind of signal may be used to monitor the odour. A laboratory-made electronic nose, constituted of an array of tin-oxide sensors, is used in different configurations. The ambient air is either sampled around environmental sources (landfill, urban waste composting facilities, …), or directly transferred into the sensor chamber in the field. Two main options are considered : firstly, identifying the source of odour in the background and among interfering odours and, secondly, when the malodour is recognised, trying to monitor it continuously in order, for example, to assess the nuisance or to control an odour abatement system. Chemometrics methods are generally used for both purposes. They provide quick answers and allow to evaluate the relationships between variables and between observations at a glance. They are applied on the sensor signals, eventually preprocessed by a suitable algorithm. Non-supervised analyses, such as Principal Component Analysis (PCA), provide basically a performance evaluation of the system during the development phase. On the contrary, supervised analyses, such as Discriminant Analysis (DA), or some Neural Networks algorithms are quite appropriate to make a reliable recognition in real time, when the system is developed. To predict the odour intensity, different techniques are tested : either using only one of the sensor elements, or applying different chemometrics techniques, such as Multilinear Regression (MLR) on the original measured sensor signals, Principal Component Regression (PCR), or Partial Least Squares regression (PLS). The latter seems to be the most adapted model for the intensity prediction. [less ▲]

Collecte et traitement des données relatives au suivi des odeurs du CET de Braine-le-Château 15/05/98 - 04/08/99

Report (2000)

Measurement requirements for environmental monitoring : application of the electronic nose principle.

in Fraigi, Liliana; Malatto, Laura (Eds.) IberSensor 2000 - Book of abstracts (2000)

As regards environment, the information to be provided to the decision maker or to the manager must be clear, accurate, unambiguous, and ideally it should be the result of the aggregation of a great ... [more ▼]

As regards environment, the information to be provided to the decision maker or to the manager must be clear, accurate, unambiguous, and ideally it should be the result of the aggregation of a great number of data or parameters. For example, the person in charge of the security of a municipality must have at his disposal an information of the type "all or nothing" to be able to decide if the population must be evacuated in the event of a severe pollution. However, that very simple information should be the result of a calculation based on several time series of pollutant concentration values and of meteorological data. Even the farmer who wants to know if it is the right time to spread manure without affecting too much the environment must have a single information which should be the aggregation of some complex variables. The lecture presents the concept of some "integrated index", already used to assess the quality of the environment. For example, Organic Pollution Index combines 4 laboratory measurement values of pollutants in water to make a single index characterising the global pollution in a river. Some apparatus are able to compute the integrated index "on line" and to supply directly to the user the value of the medium quality. For example, the PMV index estimates globally the thermal comfort in a building from the on line measurement of 5 parameters. FUL has designed some "smart sensors" or "smart instrument" aiming at supplying such index. Two applications are presented. The first one concerns the measurement of soil quality by means of a porous sensor combining in a single index the measurement of temperature, salinity and water contents. But the lecture develops particularly a second application which exploits the principle of the "electronic nose" to assess, in a single "signature", the quality or the intensity of an environmental odour. Such instrument, equipped with an array of "non specific" gas sensors, should be able, after a suitable learning phase, to recognise the odour source and to monitor it continuously in the field. The instrument response is thus a "pattern", similar to an integrated index, directly related to the annoyance, as felt by neighbouring people. It gives thus an information which can be handled by a manager, and which is more rich than individual pollutant concentration values. FUL has tested such instrument in the environment. The results are promising : a first design of electronic nose was able to recognise 5 odorous sources in the environment, and a portable instrument has been used to monitor the odour around a landfill site. The same concept is now tested to appraise as a whole the indoor air quality in different buildings. [less ▲]

Use of a simple tin oxide sensor array to identify five malodours collected in the field

in Sensors and actuators. B, Chemical (2000), 62(1), 73-79

A laboratory-made malodour sensing system including 12 commercial tin oxide gas sensors (Figaro Engineering) is used to identify five typical sources of olfactive annoyance: printing houses, paint shop in ... [more ▼]

A laboratory-made malodour sensing system including 12 commercial tin oxide gas sensors (Figaro Engineering) is used to identify five typical sources of olfactive annoyance: printing houses, paint shop in a coachbuilding, wastewater treatment plant, urban waste composting facilities and rendering plant. In this work, all the samples are collected in the field from real malodours in uncontrollable conditions. The ability of the system to predict the origin of unknowns odoriferous samples is investigated. The test of various pre-processing data algorithms shows that the best classification results are obtained with a parameter free of the sensor base-line. The differences in sensor responses among the five odours are shown by icon plots and confirmed by principal component analysis, which highlights four representative clusters. Classification models calibrated by discriminant analysis and artificial neural network are validated on unknowns samples. Chemical relationships between the sensors and the classification results proves that the recognition is not fortuitous. In spite of the influence of environmental parameters, results demonstrate the ability of a simple system to detect and identify typical olfactive annoyances. [less ▲]

Utilisation élémentaire d'un réseau de capteurs "SnO2" pour la reconnaissance d'odeurs environnementales

(1999, June)

Pouvoir identifier les mauvaises odeurs et les suivre en continu directement sur le terrain constituerait sans conteste un atout non négligeable pour un bon nombre d'études environnementales. Sur le ... [more ▼]

Pouvoir identifier les mauvaises odeurs et les suivre en continu directement sur le terrain constituerait sans conteste un atout non négligeable pour un bon nombre d'études environnementales. Sur le principe, un tel objectif semble correspondre parfaitement aux possibilités et à la souplesse d'un nez électronique. Cependant, si l'environnement est fréquemment cité parmi les applications possibles des nez électroniques, il faut reconnaître que les études visant la mesure des mauvaises odeurs sur le terrain restent très rares. La généralisation du concept du nez électronique au monitoring d'odeurs environnementales doit passer par la résolution d'un certain nombre de problèmes. La communication propose de mettre en évidence ces différentes limitations et problèmes. L'étude présentée pour illustrer ce propos est relative aux odeurs provenant de 5 sources typiques de l'environnement. Elle montre qu'un appareillage simple, utilisé sans grande précaution et sans trop se soucier de la reproductibilité des conditions d'échantillonnage parvient à identifier correctement l'origine des odeurs qu'on lui propose. [less ▲]

Identification of pollutant gases with a multisensorial arrange.

in Weimar, Udo (Ed.) proceedings of ISOEN 99 (1999)