Odours are a mixture of light and small molecules which, stimulated by the human senses are perceived as an odour.
Odour assessment is a key point and a problem facing many industrial processes such as Refineries, Slaughterhouses, Distilleries, Landfills, Waste Water Treatment plants and Anaerobic Digestor Plants.
Due to growing concerns over the environmental impact and human well being along with complaints submitted to regulators and governing bodies, installations that cause smells are required to have effective odour controls in place.
SAL routinely provide two different analytical approaches to assist with odour assessments:
1. VOC analysis by GC/MS TD
A grab sample is collected into a gas bag and upon receipt pre-concentrated onto a thermal desorption tube. Subsequent analysis is carried out by Gas Chromatography Mass Spectrometry using Thermal Desorption. A complete list of substances and their concentrations are produced and the Odourous compounds detected are compared against a database which lists the odour threshold levels.
A grab sample is collected into a bespoke Nalophan sampling bag provided by SAL. To establish the odour concentration, an olfactometer test is used, which employs a panel of human noses as sensors. In the olfactometry testing procedure, a diluted odorous mixture and an odour-free gas (as a reference) are presented separately from sniffing ports to a group of panel members, who are housed in an odour-neutral room. They are asked to compare the gases emitted from each sniffing port, after which the panel members are asked to report the presence of odour. The gas-diluting ratio is then decreased by a factor of two (i.e. chemical concentration is increased by a factor of two). The panel members are then asked to repeat their judgement. This continues for a number of dilution levels. The responses of the panel members over a range of dilution settings are used to calculate the concentration of the odour in terms of European Odour Units (ouE/m3). The method is based on dilution of an odour sample to the odour threshold (the point at which the odour is only just detectable to 50 % of the test panel).