The quantification of emission rates and the impact of odour on individuals is often a difficult task. The strength of odours is measured in odour units (o.u.) and is defined as that quantity of odorous substances which, when dispersed in one cubic metre of air, becomes just detectable by half of the human population. The human nose is the most sophisticated odour sensor known. Odours have many adverse impacts including; interference with everyday activities, feelings of annoyance, physical symptoms of nausea, headache or affected breathing, complaints to authorities, and direct individual action to modify the environment (shutting windows, installing air conditioners, masking with the use of deodorants, moving out of the area).