Odour impact criteria, i.e. a combination of an odour concentration
threshold value and a tolerated exceedence probability, are
used in many countries to determine separation distances between
odour sources and residential areas to avoid odour nuisance. A
selection of different national odour impact criteria is summarized
for European countries, for U.S. states, Australia and NewZealand in
Sommer-Quabach et al. (2014) and Piringer and Schauberger
(2013). A discussion whether the different national odour impact
criteria to protect the same land use would result in similar separation
distances is found in Sommer-Quabach et al. (2014). The
peak-to-mean factor used to account for the short-term reception
of odour by the human nose varies from country to country and can
take on values between 1 and 10. All countries except Austria use
either 1 (no peak-to-mean effect) or a constant value. In Austria, the
peak-to-mean factor is assumed to be stability-dependent and to
decrease with increasing distance from the source, caused by turbulent
mixing. Consequently, the decrease is strongest for unstable
stratification and is less pronounced the more stable the stratification
is estimated. A discussion of this concept against constant
peak-to-mean factors is available from Schauberger et al. (2012).
They demonstrate that the peak-to-mean factor depends on several
parameters, like stability of the atmosphere, intermittency, travel
time, or distance from the source. The assumption of a constant
peak-to-mean factor can therefore only be used as a very rough
estimate.