  Localisation of a source of a toxic release of biochemical aerosols in the
atmosphere is a problem of great importance for public safety. Two main
practical difficulties are encountered in this problem: the lack of knowledge
of the likelihood function of measurements collected by biochemical sensors,
and the plethora of candidate dispersion models, developed under various
assumptions (e.g. meteorological conditions, terrain). Aiming to overcome these
two difficulties, the paper proposes a likelihood-free approximate Bayesian
computation method, which simultaneously uses a set of candidate dispersion
models, to localise the source. This estimation framework is implemented via
the Monte Carlo method and tested using two experimental datasets.
