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 OU_E m⁻³), higher odour concentrations resulted from the cut surface of grass silage (3990 OU_E m⁻³) and maize silage (1690 OU_E m⁻³) in the stores as well as from the mixed ration with silage on the feed table (2955 OU_E 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 OU_E m^-3) than littered areas such as cubicles and deep-bedded areas (<500 OU_E m⁻³).