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Aerosol Instrumentation (Inertia-Based)


:: Section 1


Impaction has extensive application in the collection and measurement of aerosol particles. In the first half of the 20th century, impaction was a common method for collecting dust for the evaluation of occupational environments.

Sampling an aerosol with an impactor can provide information about its particle size distribution. The mass of the particles collected on the impaction plate and of those collected on the filter downstream the impaction plate are determined by weighing them before and after sampling. The impactor separates the particulate mass into two particle size ranges: particles larger than or smaller than a certain cutoff size. The collected aerosol can further be analyzed for various properties such as chemical composition, shape, and toxicity using other analytical instrumentations.

Two common types of impactors are discussed in this module: cascade impactor and virtual impactor. Another inertia based instrument, Time-of-Flight, is also included. The objective of this module is to help understand the principles of inertia-based aerosol instrumentation and the factors that affect the cutoff size of an impactor. For the principles of inertia, please review the module of Aerosol Transport.


Environmental Engineers American Academy of Environmental Engineers
Chemical Engineers American Institute of Chemical Engineers
NIEHS National Institute of Environmental Health Sciences

Valuable Reading:

  • W. C. Hinds, Aerosol Technology, 2nd Edition, Wiley Interscience.
  • P. A. Baron and K. Willeke, Aerosol Measurement: Principles, Techniques, and Aplications, 2nd Edition, Wiley Interscience.