Aerosol Instrumentation (Inertia-Based)

:: Section 5

Virtual Impactor

For virtual impactor, the impaction plate is replaced by a collection probe. Particles with sufficient inertia are thrown into the collection probe. These particles remain airborne and are carried by the minor air flow onto a filter. Smaller particles are carried radially away from the jet axis by the major air flow and avoid the collection probe. These particles are collected on a downstream filter. Thus, in a virtual impactor, particles larger than and smaller than the cutoff size are collected on separate filters.

Figure 3. Schematic diagram of a virtual impactor