Particle-Molecule Collection by Sonic Flow Impingers

The information presented in this paper is directed to those industrialists and researchers interested in molecule and near micron and submicron particle sampling by a convenient, inexpensive, and sufficiently accurate method. The use of two sonic flow impingers in series is predicted to collect 98-99% of a phosphoric acid aerosol having a mass median diameter of 0.7 p. The first impinger of a new design is shown, in field sampling, to collect simultaneously 90-98% of the aerosol and 95% of molecular fluoride compounds. On the same aerosol, the standard Greenburg-Smith impinger shows a low collection performance, less than 50% at 1 cfm and 65% at sonic velocity. The use of a first impinger at sonic flow greatly simplifies sampling procedures by eliminating the need for a test meter and associated pressure and temperature measurements. Also, for small particle sizes isokinetic sampling is not necessary and sampling line losses by deposition are shown to be less than 1%. The low initial cost of the sampling units and the low manpower requirements for setting up and supervising sampling make possible the taking of a number of samples sufficient to establish emissions over extended intervals of time. The equipment is especially suited to locations having multiple emission sources, or for locations requiring simultaneous sampling of many points.