Nalophan bags are commonly used for air sampling and especially for odour analysis. Even if olfactometric measurement must be carried out within maximum 30 hours after sampling, the question of potential sample evolution is always present. This study illustrates the behaviour of selected sulphur compounds in Nalophan bags from filling to analysis (over a period up to 100 hours).

   Select compounds were hydrogen sulphide, carbon disulphide, methyl mercaptan, ethyl mercaptan, dimethyl sulphide, diethyl sulphide and dimethyl disulphide and tested at high concentration level (in a range of 3900 to 1800 ppb each) to facilitate their direct and quick measurement by gas chromatography with flame photometric detector. The chemical analysis shows losses by adsorption and by diffusion depending on time and other conditions. Even if the variation seems limited during the first hours, the evolution shows that the need for a better film is real. 

   Cattle farms consist of various spatially extended odour-emitting areas representing ground-level diffuse odour sources. These include loose-housing systems with outdoor exercise areas, the supplied diet, and storage areas for silage, slurry and solid manure. The aim of this study was to identify relevant odour sources on cattle farms and to compare the odour concentrations of individual sources, bearing in mind descriptive parameters.   

   Compared with hay and sugar beet pulp (mean: <750 OUE m−3), higher odour concentrations resulted from the cut surface of grass silage (3990 OUE m−3) and maize silage (1690 OUE m−3) in the stores as well as from the mixed ration with silage on the feed table (2955 OUE m−3). Samples from the solid floors in the cattle housing (feeding and cubicle access aisles, outdoor exercise area) and from solid manure stores showed higher odour concentrations (1485 resp. 1845 OUE m-3) than littered areas such as cubicles and deep-bedded areas (<500 OUE m−3).

historyTOSeries   As many of you already know, the EN 13725 was published in February 2022. There are many new provisions in the new text that needs to be reviewed in detail, but maybe one of the most impacting in the day-to-day operations of the over 400 laboratories around the world is the one of the minimal recovery rate accepted for olfactometers.

   With the new standard in hand, no olfactometer can be used for odour measurement under the EN 13725 accreditation scheme, unless recovery rates of 70 % or higher has been tested for four test gases: hydrogen sulphide, n-butanol, propanoic acid and dimethyl sulphide. That means that any olfactometer in the world needs to pass this test if an accreditation is needed. And this is no cheap test.

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