An aerodynamic aerosol classifier (AAC) is an embodiment of a measurement technique for classifying

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be generated from natural or Human impact on the environment, human causes. The term ''aerosol'' co ...

particles according to their

aerodynamic diameter An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be generated from natural or human causes. The term ''aerosol'' commonly refers to the mixture of particulates in air, and not to the par ...

s. The technique allows online size classification of particles without requiring them to be electrically charged, and advantageously allows selection of particles within a narrow range of aerodynamic diameters. This is by contrast to an impactor or virtual impactor, which allow only particles smaller than, or larger than, a certain cut-point, respectively. A practically implementable AAC can classify particles from the nanometre range to a few microns in size. This removes many of the difficulties associated with multiple charging artifacts, such as may be encountered when classifying particles by size according to

electrical mobility Electrical mobility is the ability of charged particles (such as electrons or protons) to move through a medium in response to an electric field that is pulling them. The separation of ions according to their mobility in gas phase is called ion ...

(such as the differential mobility analyser or DMA). The selection of particles by aerodynamic diameter also lends itself to respiratory and

inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

applications as this metric directly affects lung deposition. The technique is described by Olfert et al.

Scanning aerodynamic size spectrometer

A scanning aerodynamic size spectrometer (SASS) uses a

condensation particle counter A condensation particle counter or CPC is a particle counter that detects and counts aerosol particles by first enlarging them by using the particles as nucleation centers to create droplets in a supersaturated gas.Aerosol Measurement: Principle ...

(CPC) downstream of an AAC to measure high resolution aerodynamic particle size distributions (APSD). The AAC's rotational speed is ramped up or down, continuously changing the size of particle passed, whist the CPC counts the particles. An inversion algorithm takes into account the particle residence timings in the classifier and in the CPC to produce the final size distribution. The technique is similar in principle to the

scanning mobility particle sizer A scanning mobility particle sizer (SMPS) is an analytical instrument that measures the size and number concentration of aerosol particles with diameters from 2.5 nm to 1000 nm. They employ a continuous, fast-scanning technique to provide ...

(SMPS), which instead produces an

size spectrum, although the SASS inversion does not need to take account of particle charge state. The SASS was first described by Johnson et al.

References

{{Reflist Aerosols Aerosol measurement