THE PRE-IMPINGER - A SELECTIVE AEROSOL SAMPLER

Journal/Book: Brit. J. industr. Med. 1953 10 142.. 1953;

Abstract: From the Microbiological Research Department (Ministry of Supply) Porton Wilts (RECEIVED FOR PUBLICATION MARCH II 1953) Summary A simple device is described which when fitted to the front of an impinger divides the total aerosol sample into two particle-size fractions by means of size-selective impingement into liquid. The cut-off between the two fractions is set at 4 µ to simulate nasal penetration. The curve of efficiency of impingement of particles into the liquid against particle size shows that the pre-impinger has a very high efficiency in relation to its jet velocity. This is due to a double impingement process an the liquid surface. The particle intake efficiency at various wind speeds is given in detail and is shown to be good for particles smaller than 30 µ. Empirical equations are given to show the relation between cut-off size intake hole diameter and jet velocity so that the cut-off may be set to any other desired figure in the range 22 1/2 µ to 8 µ. Internal losses were evaluated and shown to be small. Streamlines of flow into and around the device were investigated by means of smoke filaments in a wind tunnel. It is concluded that the particle retention of the pre-impinger is similar to that of the nasal passages while the material in the backing impinger is similar to that reaching the lungs. The pre-impinger appears to have some important advantages over other devices for selective sampling such as dry impaction systems elutriators and settling chambers. ___MH

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