The `Conifuge' - A Size-separating Sampling Device for Airborne Particles

Abstract

An apparatus for sampling airborne particles is described, consisting basically of a conical self-pumping centrifuge, in which the indrawn cloud is `winnowed' by an internally circulating stream of clean air in such a way that the particles are classified according to their settling velocities and deposited on a glass slide in a continuously graded sample. When the particles are of similar shape and density, the settling velocities are a unique function of the size, and the deposite is in the form of a spectrum of particle sizes with a high degree of purity. For spherical particles of unit density, the spectrum extends from about 30 to 0.5 μ diameter. The apparatus is normally driven by an electric motor at a speed of 3000 r.p.m. and samples air at a rate of 25 c.c./min.