Development of an Experimental Setup to Measure the Effectiveness of Mechanical Filters For Nanoparticles

Nanoparticles (NPs) are particles of less than or equal to 100 nm in diameter. Due to their size, they have a significant effect on health and safety of people. Capture of these NPs in general ventilation systems by filters remains one of the most widely used means of protection due to its relative simplicity of implementation and its effectiveness for capturing various size of particles. In North America, filters used in general ventilation systems are tested by the ANSI/ASHRAE Standard 52.2 and are graded according to their efficiency, which is a function of particle diameter. However, the current standard limits the filtration efficiency assessment for particles between 0.3 and 10.0 microns. There is therefore a significant lack of knowledge about the behavior of these filters with respect to the particle diameter below 0.3 μm. The main objective of this study was to develop a measurement procedure to evaluate the effectiveness of mechanical filters used in general ventilation systems against (NPs). In this regard a small setup was designed, build and qualified. Then measurement procedure was validated by comparing the penetration measurements with those obtained on qualified big loop setup, which was inspired by ASHRAE setup for nano-metric particles. One type of mechanical filter rated (MERV 8) in three depth sizes (1, 2 and 4in) is used to illustrate the full penetration range that can be measured on both setups. The obtained results are consistent with the classical filtration theory for mechanical media and with previous experimental measurements on media and filters. The data presented in this study show that the particle range of 22.1-294.3 nm gives a fairy good correlation (R2=0.898) between the two setups and for the penetration range of 0.7-1.0 at two face velocities of: 1 and 0.75 m/s. The outcome results from this study is a firm validation to evaluate the effectiveness of mechanical filters used in general ventilation systems against nanoparticles