[en] The principle of the real time determination of air voluminal activity from the measurement of the activity of the filter. The ''Pu'' measurement processing has to comple the Pu/natural radioactivity discrimination that the sampler cannot do alone. The basic process of the measurement processing is described. For the operation checkout and the examination of performance of the processing, and for the technical success of a measurement-processing system, it is possible to use a real-time simulation of the different sensors; in the case of ''Pu'' processing, a mockup of the sampler has been prefered; it gives the elementary countings due to the natural radioactivity for the two ''Pu'' and ''RaA'' windows; it has been associated to a simulator giving the pulses corresponding in the ''Pu'' window to only ''Pu'', according the chosen profile. The main results obtained after several hundreds simulations are given; eight diagrams, quite representative, are presented. To concludes the performence of the BFSA monitor, for plutonium aerosol monitoring, in which the TMAPU2 measurement processing system and a performant detection head are associated, are reviewed