Assessing the effectiveness of filtering masks during exposure to nanoparticles

The primary objective of the study presented in this article is to put in place a method of measuring the protection offered by Respiratory Protective Devices (RPDs) in the event of exposure to nanoparticles. A secondary objective is to measure the protection for filtering masks in order to highlight any specificity due to nanoparticles. The nanoparticles test bench (ETNA), dimensioned for the needs of testing at IRSN (French Institute for Radiological Protection and Nuclear Safety), has made it possible to test the performance of two half-masks for nanoparticles of diameter lying in the range 5 nm to 100 nm. The findings show the very considerable reduction in overall effectiveness of the half-mask compared with that of the filter alone, due to leaks between the device and the face. Such leaks can be quantified in terms of flow rate and compared from one model of mask to another. It also appears that continuous flow tests do not take into account the effectiveness of such protective devices for human breathing (cyclic flow). Prospective tests on volunteers at INRS have confirmed these results and give an initial illustration of the protection factors of various types of RPD in protecting against nanoparticles.