We used three gas sensors to monitor hydrogen sulfide, ammonia, and volatile organic compounds (VOCs), which were frequently emitted from environmental facilities, such as municipal wastewater treatment, livestock manure treatment, and food waste composting facilities. Two electrochemical (EC) sensors for detecting hydrogen sulfide and ammonia, and a photoionization detector (PID) sensor for detecting VOCs were characterized in this study. The performance of their linearity by concentration levels, lower detection limit (LDL), repeatability, reproducibility, precision, and response time were tested under the laboratory condition. The linearity according to concentration levels were favorable for all three sensors with high correlation coefficients (R2 > 0.98). The ammonia sensor showed the highest LDL (18.6 ppb) and the hydrogen sulfide and VOC sensors showed 22.3 ppb and 26.7 ppb of LDL, respectively. The reproducibility and precision were favorable for all three sensors, indicating a lower relative standard deviation (RSD) than 0.9% in the reproducibility test and 7.2% in the precision test. The response times to reach target concentration were varied from 1 to 12 minutes. The ammonia sensor needed 12 minutes of response time at 1 ppm target the NH3 concentration and the hydrogen sulfide and VOC sensors needed less than 2 minutes of response time.

In this study, the odor generated in a livestock farm with 500 heads of finisher breed in 661 m² was monitored during 6 months using a gas sensor, a wired / wireless communication system and database server. Odor unit, ammonia, hydrogen sulfide, and total volatile organic compounds (TVOC) were monitored using the gas sensor. To show the tendency of odorous substances generation, the odor concentration was shown in the graph on a monthly and daily basis. Among the analysis items, the maximum generation of odor was found to be closely related to the generation of hydrogen sulfide. Through observing the daily and monthly trends of odor substances, it was found that each substance was a useful indicator for monitoring odor, because ammonia, hydrogen sulfide, odor and TVOC were increased and decreased in a similar pattern. The odors were highest in the hours of the early morning (00:00-05:00), the evening (18:00-23:00), and the morning (06:00-11:00) in a day. After the use of the microbial agent was discontinued in autumn (October), anaerobic digestion of the manure in a pit proceeded and the amount of hydrogen sulfide increased. Therefore, despite a slight decrease in ammonia production, the odor unit level did not decrease after October but rather was somewhat increased. In the future, the use of the odor monitoring system is expected to improve the efficiency of odor sources management.

The purpose of this study is to produce an adsorbent material with biomass by-product that are readily visible in daily life. The biomass by-product used in the study are coffee grounds, oak leaves and chestnut peels. These biomass by-products were produced with dry, carbonization and activation treatments. The equipment for the evaluation of adsorption capacity was the batch type system to measure the concentration of test gases with the odor sensor device. Biomass by-products have been shown to improve the absorption characteristics of adsorbent through carbonization and activation. The adsorbent made with coffee grounds and chestnut peels had superior adsorption capacity to hydrogen sulfide (H2S) and complex odor (H2S & NH3) in a comparison with regular activated carbon. The odor sensor device could be used to evaluate the device of adsorption capacity of the adsorbent.

The study analyzed performance assessment factors of VOCs odor sensors from 3 different manufacturers, such as minimum detection limit, humidity stability and temperature stability. Through the minimum detection limit assessment, it was found that a VOCs sensor was able to detect TVOCs at the concentration of 5 ppb. The standard deviation ratio was over 10%, and it increased as humidity rose. The range of temperatures in which the VOCs odor sensor using photoionization could operate was between 25oC and 40oC, and the sensor output values were unstable at low temperatures. In terms of the temperature stability of the metal oxide semiconductor sensor for measuring complex odors, the sensor output values dropped considerably to 0~10oC, and were similar to the concentrations of odorous gases generated at 25oC. The results of the test of VOCs odor sensor outputs after temperature and humidity pre-treatment revealed that the respective stable output values at 50% humidity and 25oC were similar to the concentrations of manufactured odors. In terms of temperature and humidity stability of the VOCs odor sensors, all target VOCs substances had stable output values at 25oC to 40oC and at 50% to 65% relative humidities, and unstable values at low temperatures and high humidities. Therefore, the implementation of pre-treatment systems including temperature and humidity correction (25~40oC, 50~65% RH) is required for the stable use of VOCs odor sensors.

The correlation analysis between odor sensor and air dilution olfactometry method with odor emission facilities was performed for the real-time evaluation of odor emitted from the 13 facilities. The total correlation was less significant for all facilities due to various emission characteristics of odor. The correlation for the individual facility, however, showed a higher correlation coefficient (R=0.7371~0.9897). Especially, the strong correlation (above 0.9) was observed for the industry type with the odor characteristics like tobacco, styrofoam, acetic acid, and burning smell. The repeated odor measurements using the odor sensor showed good reproducibility with the mean relative standard deviation of 5.06%. The odor sensor could be useful tools for identifying and evaluating odor with an olfactometry in field, if the use and proofreading of the odor sensor are improved by a standardized method.

The study analyzed performance assessment factors of odor sensors from 4 different manufacturers, including minimum detection limit, humidity stability and temperature stability. In the minimum detection limit assessment, only one electrochemical gas sensor was able to detect ammonia and hydrogen sulfide at the concentration of 5 ppb. The standard deviation ratio was over 10%, and it increased as humidity rose. The range of temperatures in which the electrochemical and photoionization gas sensors could function well was between 25oC and 40oC, and the sensor output values were unstable at low temperatures. Regarding the temperature stability of the metal oxide semiconductor sensor for measuring complex odors, the sensor output values dropped considerably to 0~10oC, and were similar to the concentrations of odor gases generated at 25oC. The results of the test of odor sensor outputs after temperature and humidity pre-treatment revealed that the respective stable output values at 50% humidity and 25oC were similar to the concentrations of manufactured odors. In terms of temperature and humidity stability of the NH3, H2S and Complex odor sensors, all target substances had stable output values at 25~40oC and 50~65% relative humidity, and unstable values at low temperatures and high humidity. Therefore, implementing pretreatment systems including temperature and humidity correction (25~40oC, 50~65% RH) is necessary for the stable use of odor sensors.

In this study, odor sensors were evaluated in two areas, which were reproducibility of measurements and linearity and correlation of results. The evaluation of linearity and correlation showed that the linearity of the measurement object substance at low, medium and high concentrations of all intervals, and correlation (R2) also appeared to be quite high, at 0.8 to 0.9. Specific performance evaluation results of ammonia, hydrogen sulfide, TVOC and complex odor sensor to the individual substances are somewhat different, but the result have able tendencies. All odor sensors showed detectable in all metrics at 5 ppb concentration in temperature 25oC, humidity 50%. However, there is needs to be determined that in many cases the standard deviation is 10% or more in 5 ppb, and reproducibility appears in the high concentration region with a standard deviation of less than 10%. Because complex odor sensor (MOS sensor) output value is relatively accurate concentration value for the odor and the reaction was stable, MOS sensor is to be considered methods for measuring the complex odor. Reactivity of ammonia, hydrogen sulfide and TVOC odor sensor to the concentration of individual odor substances stably displayed, but the reactivity of the mixture material showed the same trend, however, the hydrogen sulfide and TVOC sensor reactivity were unstable. There is thus a need to maintain the proper temperature and humidity environmental operating condition of odor sensors.

In this study, a correlation analysis of odor was performed in order to assess the reliability and the field applicability of the Odorous gas sensor for continuous real-time monitoring. Hydrogen sulfide was found to have a correlation of 41.5~65.8%, and Ammonia is was found to have very low correlation in less than 200 ppb concentration. Reactivity evaluation result, hydrogen sulfide is the reactivity was higher than the low concentration condition of 100 ppb or less indicated by 31.3~36.4% in the 100 ppb or more high density condition based on the reference density value. For ammonia was very low reactivity in the low-concentration conditions below 200 ppb. TVOC and composite odor assessment did not occur Reactivity no reference concentration value, the specific comparison between both sensors showed a similar trend. In the same Odorous gas sensor accuracy between the result, 40.3~130.6% hydrogen sulfide, ammonia, 69.1~104.9%, TVOCs is 24.7~98.6%, exhibited human odor intensity from 5.5~33.2%.

This study was carried out to investigate the response characteristics of a hydrogen sulfide electrochemical gassensor for several wastewater odors. At first, it was found that bubbling sampling method was superior toheadspace sampling method in terms of sensor sensitivity. High correlation between odor concentration and sensorresults was shown for two wastewater which were r=0.977 for food-waste recycling wastewater and r=0.997for food industry wastewater. On the other hand, no correlation (r=0.258) was found for plating wastewater,because hydrogen sulfide was not the main odorant for that.

This study evaluated the concentration(OU/m3) of a complex odor being discharged from tire, feedstuff, bakery, paper, casting and painting manufacturing process, correlation between odor concentration(OU/m3) and the odor sensor was investigated. 4 type(A, B, C, D) gas sensors of metal oxide compounds are used in this study. Each odor sample of manufacturing process is diluted with odorless air and diluted odor samples were prepared for five different concentrations. Correlation results(R) of odor sample of tire, feedstuff, bakery, paper manufacturing process ware 0.86~0.99, and odor sample of casting, painting manufacturing process ware more than 0.93. Thus the odor concentration(OU/m3) evaluation by odor sensor was to determine the possible. In particular odor sensor B and D are likely to be effective for evaluation of odor concentration. However, odor samples before evaluation is needed the calibration process depending on the field odor sample to field apply.

In this study, odors in N industrial complex in Incheon city were measured by using air dilution olfactory method, odor sensor and instrumental analysis method. Three industry categories which are plating industry, equipment manufacturing industry and petrochemical manufacturing industry were classified and the correlation of data was evaluated based on the measurement result. The correlation coefficient between the air dilution olfactory method and the odor sensor device utilizing method in 69 points was 0.562. The correlation coefficients in the classified industry categories were observed 0.889 in the plating industry, 0.723 in the equipment manufacturing industry and 0.832 in the petrochemicals manufacturing industry. It shows that when the correlation coefficient is over 0.75, they have a strong correlation. In this result, we could identify the ease of availability of the correlation using industry classification.

This study was carried out to suggest a realtime evaluation system for the odor adsorption efficiency with electrochemical sensors. As the results of the experiments for the realtime evaluation system, the correlation coefficient between the sensor signals and the hydrogen sulfide concentration was relatively good, 0.9920 and 0.8340, respectively. The relative standard deviation of three replicative experiments for the adsorption amount in the conditions of 0.5 g and 1.0 g of adsorbent was 6.97% and 3.49%, respectively. This study would contribute the realtime evaluation of odor control efficiency to overcome the limitations of olfactory method and instrumental analysis in terms of cost and technology.

This study was carried out to estimate the usefulness of metal oxide semiconductor(MOS) sensor as an odor measuring instrument. In this study, sensor output for 12 legal malodorous compounds was measured by two kinds of the marketed MOS sensor and was investigated the correlation coefficient between sensor output and odor indicators as like odor concentration, air dilution ratio. As a results, it was estimated that MOS sensor has a high use possibility as odor measuring device for the single compound analysis, as the correlation coefficient between sensor outputs and odor concentration, R2 appeared to 0.9 or more high.

The application of gas sensors for the measurement of environmental odor was investigated. The test chamber systems were consist of three parts, as it were, sample injection, odor sensing and data process parts. Four type of sensors were tested with regard to sensor performance like baseline stability, sensitivity and reproducibility to H₂S, CH₃SH, NH₃, and (CH₃)₃N gases. As the results, two kinds of sensors were content with the circuit conditions used in this study. In addition, the influence of relative humidity to the selected two types sensors was tested. The [mal sensor, which was appeared to be the most stable sensor against relative humidity, was selected, and applied practically to measure the real odor from the manure odor source.

This review presents the recent developments in electronic noses (E-noses). E-noses based on metal oxide semiconductors, conducting polymers, quartz crystal microbalance and electrochemical methods have been examined with regard to several aspects, from the basic principles to the application of new products, as olfactometry sensors. E-noses consist of an array of chemical sensors, and are currently employed in the analysis of odorous compounds as well as for common gas detection. Various data analyses have been employed to establish patterns of recognition and classification techniques. Future trends and areas of application for e-noses have also been introduced and are summarized within the text.

We review basic principles and recent applications of quartz crystal microbalance (QCM) for chemical sensors. QCM sensors have been currently employed in the analysis of odorous compounds as well as common gas detection. Various types of data analysis have been employed for the pattern recognition and classification techniques. Future trends and application areas of QCM sensors is also introduced and summarized in the text.