This paper applies what is already known about the aspiration efficiency of blunt aerosol samplers at large angles to the interesting case of sampling under “orientation-averaged” conditions. This is particularly relevant to practical aerosol sampling in workplaces and the atmospheric environment. The resultant semiempirical model of aspiration efficiency contains a number of coefficients which are fitted by nonlinear regression to data sets for the human head and for two rotating-head inhalable aerosol samplers (a 3 L/min sampler intended for applications in workplaces and a 70 L/min sampler intended for particle sampling in the ambient atmosphere). Agreement for all three data sets (with 88, 64, and 37 records respectively) is generally good, with an overall R 2corr of 68%. Such semiempirical models can be useful for predicting and interpreting sampler performance until practical versions of more rigorous mathematical and numerical models become available.