The topic of the thesis is the validation of highly efficient filters built into the ventilation filtration system. The HEPA and ULPA filters are important in ensuring air quality, as microscopically small particles in the air can cause health issues or product quality problems. The first part of the thesis presents international standards, which include test methods and acceptability criteria after the installation of the filter into the ventilation system. The second part shows the validation process with an optical particle counter. The case is made on the example of sampling with static probes and on the example of a prototype filter scan. The measurement was performed on the exhaust ventilation system with a duct filter unit of the H13 filtration class. In the conclusion the efficiency of total and local filtration is calculated at a reference particle size of 0,3 micrometres.