Methods for Size-Selective Aerosol Sampling

At a Glance

Researchers at Colorado State University have developed a novel design of air sampling inlets necessary to meet sampling criteria for PM-respirable, PM-10, and PM-Thoracic aerosols appropriate to access occupational exposure and characterization of exposures to environmental aerosols.

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Respirable and thoracic mass sampling have been used for many years to assess personal exposure to particulate pollutants that deposit in the alveolar and thoracic regions of the lung. Both methods fractionate particles by aerodynamic size, so that sampled aerosol is more representative of what penetrates to the relevant regions of the respiratory tract (i.e., to mimic aerosol intake). Standards have been set that describe the relationship between aerodynamic particle diameter and sampler collection efficiency for both respirable and thoracic mass sampling, and an important design objective is to match a sampler’s performance with its standard. Many samplers have been described and evaluated in the literature are, are commercially available, and are routinely used to assess occupational exposures.

A respirable or thoracic mass sampler should meet several design objectives. In addition to performance that matches its standard, personal samplers should be small, quiet, lightweight, reliable, easy to use, and inexpensive. Battery capacity should allow operation for a suitable period. Achieving these objectives requires compromises, yet substantial progress has been made over the decades in meeting the performance objectives for these samplers.

Recently, the UPAS (ultrasonic personal aerosol sampler) was developed to address these compromises further. About the size and weight of a cell phone, the UPAS utilizes a silent piezoelectric pump and monitors temperature, pressure, humidity, light, and GPS location. A mass flow controller regulates flow, and operation is programmable. At 2 L/min, battery life is about 16 hours. Sample air flows into the UPAS through a size-selective inlet, then to a filter. The original UPAS inlet utilizes a cyclone for PM2.5 sampling and gives excellent agreement with federal equivalent method samplers for PM2.5 over a range of concentrations.

Although PM2.5 and PM10 are appropriate to characterize exposures to environmental aerosols, respirable and thoracic mass sampling are appropriate to assess occupational exposures. Because the standard for PM10 sampling is very similar to that for thoracic sampling, the same sampler might reasonably be used for both.


  • Designs are compact and readily manufacturable
  • Performance criteria for size selectivity aerosol sampling has been verified
  • Designs work with the UPAS (ultrasonic personal aerosol sampler)
  • Accurate within 5% for most dusts and mists in the workplace


  • Characterization and assessment of both environmental and occupational aerosols
Last Updated: October 2022

Collaborative or Funding Interest Welcome

IP Status

US Utility Patent Pending


John Volckens
Christian L’Orange
David Leith

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