Method for testing bacterial filtration efficacy of fabrics

A method for bringing into a required size range the Mean Particle Size of particles generated by a nebulizer in a device for testing Bacterial Filtration Efficiency of a fabric, the device comprising a nebulizer for generating an aerosol of a bacterial solution and a cascade impactor including a plurality of stages, said method comprising the steps of:

• generating an aerosol of a solution including bacteria, peptone water an NaCl;
• flowing said aerosol through the cascade impactor to provide a plurality of bacteria colonies in a plurality of plates present in the plurality of stages of said cascade impactor, characterized in comprising the steps of:
• performing a positive control run by feeding said aerosol to said cascade impactor;
• determining the Mean Particle Size of the aerosol particles based on the resulting number of bacterial colonies;
• comparing the obtained Mean Particle Size with a required range of Mean Particle Size;
• modifying the control run conditions by increasing or decreasing the concentration of NaCl in said bacterial solution and/or the temperature of said cascade impactor;
• performing at least another positive control run under said modified conditions and repeating said steps until the resulting Mean Particle Size is within the required range.