A medium is analysed for the search for an odorous biological molecule characteristic of a specific substance in an environment to be studied comprising the steps of: exposing a component containing at least one olfactory biological receptor, capable of selectively attaching the type of odorous molecule sought, to an atmosphere taken from the environment to be studied; irradiating that component by means of an incident laser radiation having a wavelength chosen in the ultraviolet close to the absorption wavelength for the olfactory receptor, to cause the excitation of a resonance Raman scattering in the irradiated component; and analysing the Raman spectrum obtained to determine whether or not it corresponds to the Raman spectrum of the olfactory receptor having attached an odorous molecule of the type sought in the atmosphere sampled, so as to identify any presence of the specific substance mentioned in the environment to be studied. The method applies particularly to the identification of toxic or hazardous substances in packaged products or objects or where access to them is difficult, for example during transit.