This part of this European Standard establishes a short-term airborne sodium chloride particle challenge test method for assessing the filtration performance of breathing system filters (BSFs) intended for the filtration of respired gases in humans. The test method is intended for BSFs used with a clinical breathing system. It is not intended for other types of filter e.g. those designed to protect vacuum sources or gas sample lines, to filter compressed gases, to protect test equipment or for physiological respiratory measurements. NOTE Non-filtration aspects of BSFs are addressed in prEN 13328-2.