Methodology for assessing the performance of urine absorbing aids in controlling malodour release.

The aim of this study was to investigate the possibility of comparing the performance of different absorbent aids in terms of odour control by discussing a suitable methodology for product evaluation. To overcome the problems of low test reproducibility owing to biological urine variability, the first step of the work consisted of the identification and the production of artificial urine having a constant and stable composition over time, moreover preventing sensorial assessors from any risk of biological contamination. Sensorial measurements were performed to optimize the similarity between artificial and biological urine, especially as far as the composition of the volatile component and therefore of the odour properties are concerned. The assessment of absorbent articles performance to control urine malodour includes both the concentration and the hedonic tone of the odour released by the article itself loaded with synthetic urine. Analyses were run on different products, which can be grouped into two different classes: absorbing aids with or without odour control technology (OCT) respectively. Results show that, despite of the presence or absence of OCT on absorbing products, their odour concentrations are almost identical, being comprised between 10 000 and 12 000 ouE m(-3) . For this reason, it is evident that odour concentration is not suitable as the sole parameter for comparison of different absorbing products. Instead, the hedonic odour tone (odour pleasantness/unpleasantness) relevant to the different product typologies (that is products with and without OCT) should be used as an additional discriminating factor for this kind of comparative tests.

Olfactory and toxic impact of industrial odour emissions.

This paper describes the approach adopted for the evaluation both of the odour impact and of the non-carcinogenic health effects relevant to odours in the city of Terni, Italy. The first part of the study focused on the quantification of emissions by means of dynamic olfactometry and chemical analyses. Dispersion modelling was then applied for the evaluation of citizens' exposure both to odours and to their non-carcinogenic toxicity. The results show that, on one hand, the odour impact is considerable, actually affecting almost the whole city of Terni. On the other hand, the toxic impact, expressed in terms of the Hazard Index (HI), is about three orders of magnitude lower than the level that is expected to bring adverse effects, over a lifetime exposure, for human health.

Validation of a method for odor sampling on solid area sources.

The aim of this paper is the study and the validation of a method for odor sampling on solid area sources. This aim is achieved by considering a suitable theoretical model that accounts for all the variables involved in the volatilization process of odorous compounds from solids into the atmosphere. The simulation of the emission of odors from a solid surface was achieved by designing a suitable experimental setup and a specific wind tunnel for laboratory tests. The results of the tests show a good correspondence between the theoretical data derived from the adopted model and the experimental data. The verification of the possibility of describing the wind tunnel functioning with a theoretical volatilization model proves the applicability of this device for sampling on solid area sources.

Evaluating the dispersion of toxic odour emissions from complex sources.

This article describes an original approach for evaluating exposure to toxic odour emissions, based on methods commonly used for assessing the impact of odour, adopted in this specific case to examine the non-carcinogenic health effects of odours in the city of Terni, Italy. First the hazardous volatile organic compounds emitted from the main odour sources were identified and quantified by chemical analysis. The Hazard Index (HI) was used to assess the toxicity associated with the emissions. The HI is the sum of the concentrations of the hazardous compounds weighted with their Reference Concentration (RfC). A RfC is the estimated continuous inhalation concentration at which people are unlikely to risk any deleterious effects during their lifetime. Atmospheric dispersion modelling was based on the Toxicity Emission Rate (TER) which, like the Odour Emission Rate (OER) conventionally used to quantify odour emissions, relates the HI with the air flow of an emission source; it is as a simple but effective method for the general characterization of toxic odour emissions in complex scenarios. The results indicated that citizens' exposure to the non-carcinogenic toxic compounds involved in odour emissions was below the level expected to have adverse effects on human health. Classical risk assessment techniques should now be employed to define the pollutants and their effects better and to validate this approach.

Improvement of olfactometric measurement accuracy and repeatability by optimization of panel selection procedures.

The EN 13725:2003, which standardizes the determination of odour concentration by dynamic olfactometry, fixes the limits for panel selection in terms of individual threshold towards a reference gas (n-butanol in nitrogen) and of standard deviation of the responses. Nonetheless, laboratories have some degrees of freedom in developing their own procedures for panel selection and evaluation. Most Italian olfactometric laboratories use a similar procedure for panel selection, based on the repeated analysis of samples of n-butanol at a concentration of 60 ppm. The first part of this study demonstrates that this procedure may originate a sort of "smartening" of the assessors, which means that they become able to guess the right answers in order to maintain their qualification as panel members, independently from their real olfactory perception. For this reason, the panel selection procedure has been revised with the aim of making it less repetitive, therefore preventing the possibility for panel members to be able to guess the best answers in order to comply with the selection criteria. The selection of new panel members and the screening of the active ones according to this revised procedure proved this new procedure to be more selective than the "standard" one. Finally, the results of the tests with n-butanol conducted after the introduction of the revised procedure for panel selection and regular verification showed an effective improvement of the laboratory measurement performances in terms of accuracy and precision.

Design and validation of a wind tunnel system for odour sampling on liquid area sources.

The aim of this study is to describe the methods adopted for the design and the experimental validation of a wind tunnel, a sampling system suitable for the collection of gaseous samples on passive area sources, which allows to simulate wind action on the surface to be monitored. The first step of the work was the study of the air velocity profiles. The second step of the work consisted in the validation of the sampling system. For this purpose, the odour concentration of some air samples collected by means of the wind tunnel was measured by dynamic olfactometry. The results of the air velocity measurements show that the wind tunnel design features enabled the achievement of a uniform and homogeneous air flow through the hood. Moreover, the laboratory tests showed a very good correspondence between the odour concentration values measured at the wind tunnel outlet and the odour concentration values predicted by the application of a specific volatilization model, based on the Prandtl boundary layer theory. The agreement between experimental and theoretical trends demonstrate that the studied wind tunnel represents a suitable sampling system for the simulation of specific odour emission rates from liquid area sources without outward flow.

Microencapsulation of menadione sodium bisulphite with polydimethylsiloxane by the spray-drying process: characterization by thermal analysis.

Menadione sodium bisulphite was microencapsulated with a polydimethylsiloxane membrane using spray-drying technology. Tests were performed using laboratory equipment and a Niro Atomizer pilot plant to scale up the process. The products were characterized with differential thermal analysis (DTA) and chemical and physical methods. Many differences between raw material and microencapsulated powder result from DTA data. The thermal characterization confirms that the spray-drying microcoating could be used to protect powder from the oxidative actions of the atmosphere.