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The present paper intends to discuss recent developments in detection and quantification of odorous compounds in real industrial gaseous emissions. In this work, the chemical characterization of industrial odours is carried out using an Agilent gas chromatograph (mod. 8890) coupled with three different detectors to obtain a more complete chemical characterization: a Mass Spectrometer (Agilent 5977B MSD), a Flame Ionization detector (FID, Agilent) and a Pulsed Flame Photometric Detector (PFPD, OI Analytical mod. 5833). This system (GC-MS/FID/PFPD) offers different significant advantages if compared with the classical analytical techniques currently adopted in the chemical characterisation of industrial odour mixtures. Applied to industrial case studies, it enables the selective detection and quantification of Volatile Organic Sulphur Compounds (VOSCs), even present in traces (ppb level) in complex gaseous mixtures, facilitating the identification of molecules responsible of odour harassment. This instrumentation represents a crucial development in enhancing the understanding of the chemical composition of odorous mixtures, demonstrating cost-effectiveness and time efficiency.

Dynamic olfactometry involves human examiners for quantifying odour. Examiners directly inhale, although diluted, the increasingly concentrated odorous samples and, during the analysis, they are thus exposed to substances potentially dangerous to human health. EN 13725 still does not propose a protocol for assessing the risk related to such activities. In the scientific literature, only few studies have addressed this issue, with discrepant approaches based on a deterministic risk assessment. However, the risk assessment needs the definition of exposure parameters that are strictly linked to their specific working time and the activity of the olfactometric laboratory, in terms of hours worked, number and type of samples analysed. Therefore, a deterministic risk assessment method remains limited to the experience of a single laboratory. Despite the importance of the topic, many aspects of the subject still remain unexplored. This paper aims to highlight the critical aspects of deterministic approaches available in the scientific literature (mainly due to the variability of exposure parameters connected with the specific working activity of every single panellist and each olfactometric laboratory and the necessity of conducting risk assessment within 30 h permitted by EN 13725) and evaluate the possible new solutions to conduct risk assessment for olfactometric workers.

The sampling of odorous emissions is a fundamental step in correctly quantifying odour concentration. Its importance was strongly emphasized in the recent Italian legislation (MASE, 2023), which describes strict constraints for conducting olfactometric sampling. In particular, for point sources, it is necessary to assess the variability of the source to evaluate any spikes in emissivity and then sample consistently with the trend of this emissivity. Therefore, this study aims to conduct a field sampling campaign that meets the criteria mentioned in the Italian recent directive, combining olfactometric sampling with continuous monitoring of the source using portable PID instrumentation. The results obtained during this preliminary monitoring campaign highlight that the variability in VOC emissions is not strictly correlated with potential variability in terms of odour concentration. Indeed, despite the variations observed in continuous measuring at the source, the odour concentration measurements remained stable throughout the monitoring period. Chemical speciation of samples identified high concentrations of propene, varying in accordance with PID reading, while the odour potential was primarily due to lower concentrations of octene and nonene, which remained relatively constant. These results indicate that continuous monitoring emission variability does not necessarily translate into odour concentration variability.

Human examiners, known as panelists, are exposed to an unknown occupational exposure risk while determining odor concentration (Cod) using dynamic olfactometry. In the literature, a few papers, based on a deterministic approach, have been proposed to establish this occupational risk. As a result, the purpose of this study is to develop and apply a probabilistic approach, based on the randomization of exposure parameters, for assessing and evaluating the occupational exposure risk among olfactometric examiners. In this methodology, the risk is assessed by computing the hazard index (HI) and inhalation risk (IR) to determine the non-carcinogenic and carcinogenic risks. To randomize the exposure parameters, a Monte Carlo simulation was described and then applied in real exposure scenario to establish the exposure risk in terms of probability. Therefore, a one-year survey of the working activity of olfactometric examiners of Laboratorio Olfattometrico of Politecnico di Milano university was conducted. Based on this data collection (exposure parameters and chemical data, divided according to sample categories), a randomized exposure scenario was constructed to estimate the probability and cumulative distribution function of risk parameters. Different distributions were obtained for different industrial samples categories and were compared with respect to acceptability criteria (the value of HI and IR at 95th percentile of distribution). The elaboration provided evidence that negligible non-carcinogenic and carcinogenic risks are associated with the panelists’ activity, according to an entire annual dataset. The application of probabilistic risk assessment provides a more comprehensive and effective characterization of the general exposure scenario for olfactometric examiners, surpassing the limitations of a deterministic approach. This method can be extended to future exposure scenarios and enables the selection of the most effective risk management strategies to protect the health of olfactometric examiners.

This work aims to present the applicability of a gas chromatograph equipped with three detectors for the analysis of odorous mixtures. An Agilent gas chromatograph (mod. 8890), equipped with a mass spectrometer (Agilent 5977B MSD), a Flame Ionization Detector (FID, Agilent) and a Pulsed Flame Photometric Detector (PFPD, OI Analytical mod. 5833) was adopted, obtaining simultaneous acquisition with MS, FID and PFPD detectors. The splitting of the sample into the three detectors was carried out at the end of the chromatographic column, by a capillary flow technology splitter (Agilent Splitter CFT). By using this system, it is, therefore, possible to achieve the specific detection and quantification of organic compounds by FID analysis, sulphur compounds by PFPD and the identification of the compounds by MS analysis, via comparison with mass spectra. Based on the preliminary outcomes obtained,the application of this system in the analysis of odour samples enabled the determination of specific classes, even in traces: by this, the subsequent identification of these compounds during a single chromatographic run is possible. This combination provides significant time and costs savings in the calibration and analysis of chromatographic data.

An odour sample is generally a complex matrix consisting of numerous molecules (mostly volatile organic compounds, VOCs) chemically different from each other, and which can be perceived by the human nose. In order to chemically characterize this complex gaseous matrix, gas-chromatography (GC) is commonly used. By this analytical technique, it is possible to obtain the resolution of odour gaseous mixtures in order to qualify and quantify the compounds. However, the quantification is a tricky operation based on the comparison of the sample under examination with purpose-made gas mixtures containing a compound, chosen as a standard, at known concentration. Commonly, these mixtures are obtained from cylinders of compressed gases, the use of which involves problems relating to their management, thermodynamic equilibrium feasibility, considerable economic outlay and not-negligible procurement times. This paper describes a method, proposed as a versatile and simple alternative to the use of such cylinders, for preparing gaseous calibration standards at known concentration. The method involves the continuous injection of VOC in liquid form, by means of a syringe pump, into a stream of neutral gas, such as air or nitrogen, which acts as diluent gas, controlled by a mass flow meter. Exploiting the volatility of the compounds used, it is possible to generate a continuous gas stream, exiting the system, containing the selected VOC at the desired concentration, which can be directly used as calibration standard.

Different techniques have been developed for the analysis of gaseous sulphur pollutants, to maximize the analytical signals. In a complex matrix, such as odorous emissions, the detection of sulphur compounds can be critical in GC analysis, due to the lower concentration of these pollutants and the disturbing effect of co-eluting hydrocarbons. However, their detection is fundamental because they have a non-negligible odour impact. In the field of gaseous emissions analytics, it is common to use sorbent tubes for the sampling step. This technology uses different adsorbent materials, with different selectivity depending on the nature of the gas to be analysed. This work aims to evaluate the ability of three different sorbent tubes to collect different sulphur compounds, belonging to the classes of mercaptans, thioethers and aromatic heterocyclic compounds. A standard solution of 10 sulphur compounds was prepared by diluting in methanol 50 µL of each liquid standard into a 10 mL ?ask. Subsequently, this solution was diluted in methanol to obtain sulphur standards at five different concentrations (approximately 5-500 ng/µL). The tubes were loaded with the standard solutions with an aliquot of each solution, using a gas chromatograph packed column injector and subsequently analysed by TD-GC-MS. By the results obtained - average Response Factor (RF) and its Relative Standard Deviation (% RSD), it is possible to conduct a comparison among these tubes and evaluate their performance. From the comparison of the tubes, discussing % RSD, it is possible to highlight a slightly better performance, in terms of the number of compounds with % RSD = 30%, for tubes specific for sulphur compounds. Focusing on RF values, multi-sorbent bed tubes show slightly higher RFs for very volatile sulphur compounds, but Sulphur tubes present higher RF values for 6 compounds out of 10 compounds considered. The performance of Tenax TA tubes, instead, appears strictly correlated with the compound’s volatility and therefore they don’t appear useful for sorption of very volatile compounds.

Dynamic olfactometry is nowadays the most diffused technique to quantify odour emitted from industrial plants. The methodology, standardized by EN 13725:2003, involves human assessors, who are potentially exposed to hazardous pollutant present in odorous samples. A standardized method to evaluate the exposure risk for panellist during olfactometric analysis is not yet available. However, two different models to evaluate the occupation risk for panellists have been proposed within the scientific literature. Therefore, this paper reviews the available models and discusses their application to a real sample to estimate the occupation exposure risk for workers involved in olfactometric analyses. After a brief models’ description, these are both applied to a real odour sample, highlighting the differences between them and the most critical aspects of applying the suggested procedures for the toxicological assessment of the exposure risk for panellists. This discussion highlights that the absence of a unique standardised assessment method and uniform reference concentrations can lead to significant differences in toxicological evaluations. In addition, the presence of compounds for which no toxicity threshold is available can cause an underestimation of the minimum dilution value to be adopted to protect the health of panellists.

Nowadays, Volatile Organic Compounds (VOC) are a class of air pollutants increasingly studied in the scientific literature, due to the well-known impact on human health and the environment. They can be emitted from different sources, including various types of industrial plants, such as oil refinery and petrochemical plants. For these reasons, the attention of control agencies on VOC emissions has increased and with it the request to quantify the total amount of VOC emitted by a plant, to monitor and to reduce this emission. However, several critical aspects still exist related to the classification of VOCs and their quantification. Indeed, different definitions of VOC are reported in scientific and technical literature. These diversities result in multiple strategies for quantifying the VOCs emitted by an industrial plant. Therefore, this paper reviews the available regulation about the quantification of VOC emitted from industrial plants, focusing on refineries and petrochemical plants, to underline some formal inconsistencies in VOC estimation procedures. From this comparison, it appears clear that VOC quantification can be addressed in different manners, obtaining a substantial non-uniformity of the VOC emission data. The data difference can conduct to a misleading estimation of emission rate.

Refineries are characterized by relevant odour impacts, and the control and monitoring of this pollutant have become increasingly important. Dynamic olfactometry, a sensorial analysis that involves human examiners, is currently the most common technique to obtain odour quantification. However, due to the potential presence of hazardous pollutants, the conduction of occupational risk assessment is necessary to guarantee examiners’ safety. Nevertheless, the occupational risk for olfactometric examiners, specifically correlated with oil refineries emissions, has not been investigated yet. Therefore, this paper applies a new methodology of risk assessment for workers involved in dynamic olfactometry, focusing on odorous refineries emissions. The chemical characterization of refinery emissions was obtained by TD-GC-MS, analysing odorous samples collected at different refinery odour sources. A database of chemical pollutants emitted from a refinery plant was built up, and the minimum dilution values to be adopted during the analysis of refinery odorous samples was calculated. In particular, this evaluation highlighted that, in this scenario, a non-negligible carcinogenic risk may exist for panellists exposed to refineries’ samples, and the carcinogenic risk is sometimes higher than what is acceptable. Therefore, a minimum dilution value between 1.01 and 5, according to the specific sample, must be set to guarantee the examiners’ safety.

The hazardous air pollutants (HAPs) group is composed of 187 chemicals that are known to be potentially carcinogenic and dangerous for human health. Due to their toxicological impact, HAPs are an increasingly studied class of compounds. Of the different HAPs sources, refineries are one of the major sources. In order to obtain a preliminary assessment of the impact of a refinery in terms of emissions, a useful instrument is the determination of the emission factor (EF). For this reason, this work, focusing on the USA refining scenario, aims to provide evidence for a generic trend in refinery emissions to evaluate a correlation between the plant size and the amount of its emissions, in particular the HAPs emissions. Based on the analysis of the data collected from the U.S. Environmental Protection Agency (US EPA), a general trend in the emissions from refinery plants was established, showing a positive correlation between the HAPs emissions and the refinery size, represented by a value of the Pearson correlation coefficient r close to 1. Once this correlation was highlighted, a purpose of this work became the estimation of an organic HAPs emission factor (EF): from a whole refining plant, the EF of the total organic HAPs is equal to 10 g emitted for each ton of crude oil processed. Moreover, it was also possible to undertake the same evaluation for two specific HAP molecules: benzene and formaldehyde. The benzene and formaldehyde EFs are equal to, respectively, 0.8 g and 0.2 g for each ton of processed crude oil. This work provides a simple rule of thumb for the estimation of hazardous substances emitted from petroleum refineries in their mean operating conditions.

This work aims to evaluate the non-carcinogenic health effects related to landfill odor emissions, therefore focusing on workers involved in dynamic olfactometry. Currently, the most common technique to quantify odor emissions is dynamic olfactometry, a sensorial analysis involving human assessors. During the analysis, assessors are directly exposed, at increasing concentrations, to odor samples, and thus to the hazardous pollutants contained therein. This entails the need to estimate the associated exposure risk to guarantee examiners’ safety. Therefore, this paper evaluates the exposure risk for olfactometric examiners to establish the minimum dilution level to be adopted during the analysis of landfills’ odorous samples to guarantee panelists’ safety. For this purpose, an extensive literature review regarding the pollutants emitted by landfill odor sources was conducted, comparing compounds’ chemical concentrations and threshold limit values (TLVs) to calculate the Hazard Index (HI) and thus establish a minimum dilution value. The data collected indicate that a non-negligible non-carcinogenic risk exists for all landfill emissions considered. However, from the data considered, the minimum dilution factor to be adopted is lower than the typical odor concentration observed for these sources. Therefore, the olfactometric analysis of landfill samples can be generally conducted in safe conditions.

Refineries are a major source of atmospheric emissions, which typically include CO, SO2, NOX, particulates, and volatile organic compounds (VOCs). There has been an increasing level of attention toward the emissions of VOCs related to their environmental impact as well as their potential to cause adverse effects on human health and the discomfort associated with their unpleasant odor. In general, an emission factor (EF) represents a model for a first order estimate of emissions, which correlates the quantity of pollutant released into the atmosphere with a so-called “activity index” related to the release of that pollutant. Based on the study of the scientific and technical literature regarding the Italian and European refining scenarios, an attempt was made to verify the existence of a correlation between the size of a refinery and the related total VOC emissions. Once this correlation was evaluated, it was possible to develop an emission factor for VOC emissions considering the plant capacity as the related activity index. After collecting and analyzing data concerning operative capacity and total VOCs emitted from 15 refineries in 2018, the resulting emission factor turned out to be equal to 188 ± 166 g per ton of crude oil processed. This value is in agreement with the range of 50–1000 g/ton reported in the European Best Available Techniques Reference Document for the Refining of Mineral Oil and Gas.