Indoor air quality is strongly impacted by human occupation and activity. Indeed, in indoor environment, the presence of humans causes the generation of aerosols of non-biological (cooking, cleaning…) and biological (respiration, showering…) origins. In this work we focus on the characterisation of the respiratory aerosols generated by humans in various indoor configurations. With a Biotrak (TSI), we measured the concentration of both total and viable particles for different scenarios, classrooms (30 peoples), amphitheater (150 peoples), and an experimental cleanroom Bio-E-Rates in the Certes laboratory (1 to 5 peoples). In this work, the viable to total particles (1 to 10 µm in optical diameter) concentration ratio was evaluated for the three indoor configurations cited beforehand.