Particle Sampling Bias Introduced By Anisokinetic Sampling and Deposition Within the Sampling Line

Abstract

Particle sampling errors from several sources were studied with monodisperse aerosol particles. The sources of errors investigated were the influence of the inlet probe diameter on isokinetic samples, the turbulent deposition of particles in straight tubes and one-elbow configuration, and non-isokinetic flow through the sampling probe. The sampling errors were shown to be significant for particles as small as 1 micron in some cases. A particularly significant observation was that non-uniform concentration in the conduit sampled can cause serious errors. Some studies of the particle concentration profiles in a three-inch tube showed that particles in many cases are concentrated in a narrow annulus near the wall, making representative sampling nearly impossible for these cases. The research emphasizes the need for a thorough knowledge of many particle interactions with the air system to be sampled and with the sampling arrangement chosen.