Measuring air filter efficiency down to single-digit nanometer size

Measuring air filter efficiency down to single-digit nanometer size Nanoparticles, i.e. particles with at least one dimension under 100 nm, have high mobility in airborne form and are present in large number in the air we breathe. They may pose a serious health risk because of their high mobility and increased toxicity due to the large specific surface area. They may potentially lead to new hazards or increased risks to the indoor environment occupants. Hence, the filtration of airborne nanoparticles is an important control technique as the environmental, health, and safety impacts of nanoparticles materials grow. Current standards dealing with air filter efficiency test focus on measurement between 300 nm and 10000 nm or, in the case high efficiency filters, of the minimum efficiency at the most penetrating particle size. The available knowledge and instruments provide a solid base for development of test methods to determine the effectiveness of filters in removing airborne nanoparticles down to a single-digit nanometer range, as demonstrated by recently published test methods for assessing the performance of filter media down to 3 nm.