Abstract: The invention relates to virtual impactors with slit-shaped nozzles. Virtual impactors serve to enrich aerosol particles of certain magnitudes from gases, particularly from ambient air, for the purpose of examining these particles. For very strong enrichments, reaching up to many hundreds of times the initial concentration, very effective multi-stage virtual impactors with hundreds of nozzles have been developed. However, these are difficult to manufacture and to clean. The individual nozzles can be replaced by slits which are easier to manufacture. With slit-shaped nozzles problems with instability at the ends of the slits occur. The invention describes slit-shaped nozzles, the slits of which have no ends because they are designed as curved, closed figures. By contrast with the prior art which relates to circular slits in parallel plates, here any closed figures are represented, including ones which are not in plane-parallel plates.

Abstract: The invention relates to virtual impactors with slits. Virtual impactors serve to enrich aerosol particles of certain orders of magnitude from gases, particularly from the ambient air, for the purpose of examining such particles. For very high degrees of enrichment to many hundreds of times the initial concentration very effective multistage virtual impactors have been developed with hundreds of nozzles but the latter are difficult to manufacture and clean. In principle the individual nozzles can be replaced by slits which are easier to manufacture. Since the ends of the slits cause considerable stability problems for the stream of gas the invention proposes using circular slits without ends.