Abstract: A system and process for respirator fit-testing are disclosed. The system includes conduits for taking first and second aerosol samples, from inside of the respirator mask and from outside of the mask, respectively. The samples are provided to a radial differential mobility analyzer for generating first and second modified samples corresponding to the aerosol samples. The modified samples are provided to a condensation particle counter, which generates first and second concentration values representing concentrations of suspended elements in the respective modified samples. Comparison of the concentration values yields a fit factor indicating how effectively the respirator seals against leaks. Alternative embodiment systems employ a cylindrical DMA, an electrical precipitator, or an inertial separating device in lieu of the radial DMA. For generating concentration values, an electrometer, a photometer or an optical particle counter can be used in lieu of the condensation particle counter.

Abstract: A vacuum particle detector includes a cavity providing a passage for fluid flow, a laser diode and beam shaping optics to form a substantially rectangular beam spanning the chamber. Light sensing optics, including a pair of biconvex lenses, receive light scattered when the particles suspended in the fluid intersect the beam. At least some of the scattered light is transmitted through the lenses to a photodetector. The photodetector width is selected in concert with the focal lengths of the biconvex lenses, to provide a viewing depth of field commensurate with the complete span of the beam across the chamber, whereby the photodetector responds to particles that intersect the beam over the entire span. A cone and a surrounding sleeve, both concentric about an axis of the beam, absorb the laser energy beam to provide an effective beam stop.