Summary Filtration is a simple and effective tool to capture particles of different sizes. It is one of the tools used in the occupational health and safety field to control exposure to ultrafine particles (UFPs) and nanoparticles, both in limited and makeshift working spaces and in general or specific ventilation systems. The current standard, in the case of general ventilation, limits the evaluation of the effectiveness of filtration to particles with a diameter ranging from 0.3 to 10.0 µm. Although the size of the most penetrating particles in the case of purely mechanical filters (and media) with a slow filtration speed is generally acknowledged to be 300 nm, the literature mentions a range of diameters from 100 nm to 300 nm. Since the current state of knowledge showed that in general the performance of filters based on the size of nanoparticles is still very limited, the main objective of this project was therefore to develop a measurement procedure to evaluate the performance of filters used in ventilation systems to filter particles smaller than 300 nm including UFPs. What makes this work original is the fact that it obtained reproducible effectiveness measurements as a function of size for particles smaller than 300 nm. To do this, a test bench was designed and validated and then a measurement procedure was developed to determine the performance of mechanical filters. The measurement procedure was validated by comparing penetration measures for nanometric particles on two test benches. Three different filters were used for the comparison: one rated MERV 8, one rated MERV 14 and one rated HEPA. The three filters revealed the range of penetration that could be measured on the test benches. Performance measures (penetration and pressure drop) of five filters were then obtained. The results are in accordance with classical filtration theory for mechanical media and with the previous experimental measures for media and filters. The data presented in this report show that a range from 150 to 500 nm gives one the best estimate of the diameter of the most penetrating particles, unlike a fixed diameter of 300 nm. This project was executed under the agreement between the Institut de recherche Robert-Sauvé en santé et en sécurité du travail and Concordia University to develop a research platform on the filtration of particulate matter and gases. It therefore constitutes the first step in creating the particle filtration laboratory, located at Concordia University.