Using a dispersion model to calculate ambient odour concentrations, the sep
aration distance between livestock buildings and residential areas is defin
ed by the occur impact criteria using a combination of a pre-selected odour
threshold and an exceeding probability. The dynamic Austrian Odour Dispers
ion Model (AODM), a Gaussian model, is used to calculate the direction-depe
ndent separation distances for several combinations of these two values, wh
ich represent the protection level of various land use categories. The calc
ulated direction-dependent separation distances are a function of the preva
iling wind velocity and atmospheric stability conditions. At a site in the
Austrian North-alpine foreland, the direction-dependent separation distance
(calculated on the basis of a two year time series of meteorological data)
for pure residential areas (3% exceeding probability over the year for an
odour threshold of 1 OU/m(3)) lies between 99 m (for northerly winds with a
probability of less than 3%) and 362 m (for westerly winds with a probabil
ity of 34%). For west and east the main wind directions, odour sensation ca
n be expected more often for higher wind velocities and a neutral or stable
atmosphere around sunset. Northerly and southerly winds show the typical d
iurnal variation of a local valley wind system with predominantly northerly
daytime up-valley and southerly night-time down-valley winds.