A New Miniature Respirable Sampler for In-mask Sampling: Part 2-Tests Performed Inside the Mask

This paper is the second in a series of two describing the performance of a miniature and low-weight respirable sampler designed to fit inside filtering facepiece (FFP) and half-mask type respirators. The first paper described the design of the miniature sampler and evaluated the particle and collection performance of the miniature sampler. This paper assesses its comparability with the traditional inward leakage measurement technique, and its safe use. Simultaneous mass measurements of a respirable sodium chloride aerosol were taken inside a total inward leakage chamber by a miniature sampler and by sodium flame photometry. Direct side-by-side comparison of the two methods yielded excellent correlation (R ² = 0.99), as did comparison when sampling from inside four different masks when worn by a breathing Sheffield dummy head. In addition, comparison tests were carried out using three models of FFP worn by human volunteers both with and without the miniature sampler, in order to test whether or not the presence of the miniature sampler negatively affected the protection offered. The difference between the tests carried out with the miniature sampler and without the miniature sampler was not statistically significant (P = 0.3). In all cases, the masks performed within their protection class, whether the miniature sampler was fitted or not. We therefore conclude that the miniature sampler does not significantly affect the protection offered by the masks. The miniature sampler may prove a viable option for in-mask measurements of respirable dust where low air concentrations of hazardous material are expected.