A homogeneous allergen-laden atmosphere of chosen concentration and chosen MMAD is created by means of an ultrasound nebulizer (9), an aqueous composition of allergens (8) and a stream of pure air (13). To this end, the concentration and flow rate of the allergen composition and the frequency of the nebulizer are calculated, allowing these parameters to be obtained. The nebulizate obtained is mixed with the stream of pure air outside the exposure room (2). The resultant stream is introduced into the exposure room by diffusion outlets (21) positioned high up, and is sucked out by one or more discharge outlets (22) positioned close to floor level. Particular measurements are continuously monitored to ensure that safety thresholds are not exceeded. Prior to that, the efficiency of the nebulizer is measured, the concentration and MMAD of the allergens obtained in the exposure room are checked and the distribution of the stream is homogenized by adjusting the opening of each discharge outlet.
