Design, calibration and testing of a parallel stage impactor

Area of Science:

• Aerosol science and technology
• Environmental engineering
• Particle characterization

Background:

• Traditional cascade impactors face limitations in determining accurate mass or chemical size distributions of aerosols.
• Parallel-stage impactors present a promising alternative for improved aerosol fractionation.
• Accurate aerodynamic particle sizing is crucial for understanding aerosol behavior and impact.

Purpose of the Study:

• To design, manufacture, calibrate, and test a novel seven-stage, round jet impactor based on the parallel stage concept.
• To evaluate the performance of the parallel-stage impactor for fractionating airborne particles by aerodynamic diameter.
• To assess the advantages of this parallel design over conventional cascade impactors for aerosol analysis.

Main Methods:

• Development of a seven-stage, round jet impactor operating at 25 liters per minute.
• Utilized a novel calibration technique with polydisperse aerosol to determine stage cut-off sizes (0.35 to 7.0 micrometers aerodynamic diameter).
• Tested for particle bounce and blow-off using urban aerosols and examined impaction surfaces microscopically.

Main Results:

• The parallel-stage impactor successfully fractionated airborne particles into distinct aerodynamic size ranges.
• Calibration results confirmed stage cut-off sizes closely matched theoretical predictions.
• Particle bounce and blow-off were minimal, with particles embedding into the adhesive surface, ensuring sample integrity.

Conclusions:

• The designed parallel-stage impactor provides significant advantages for determining aerosol mass and chemical size distributions.
• The device demonstrates reliable performance and accuracy in aerodynamic particle fractionation.
• This impactor represents an advancement in aerosol sampling technology, offering improved data quality for environmental and health studies.