Ultrafine particle monitoring for air quality measurements
Dec 02 2020 Read 905 Times
Air quality affects us all. While the field of air quality encompasses many aspects, one topic that is been gaining attention in recent years is the measurement of ultrafine particles.
What are ultrafines?
Ultrafines are particles that are too small to contribute appreciably to mass-based measurements, but are present in ambient air. They are quantified using the concept of ‘number concentration’, or number of particles per cubic centimeter of air. For more on number-based measurements, please refer to our whitepapers on ambient air quality.
Measuring ambient particle number concentrations
Measuring the particle number concentration of particles in ambient air is mainly done using a single particle counting technique, and focuses on particles in the size range of ~1 nm to ~1 μm. This technique utilizes a condensation process to make those tiny, invisible particles visible to an optical counter. These Condensation Particle Counters (CPCs) work over a wide range of concentrations, and can therefore be used both in heavy polluted areas and at background stations. The European standard CEN/TS 16976 describes the use of CPCs to determine atmospheric aerosol number concentrations, while CPC calibration is described in ISO 27891:2015. CPCs are fully automated systems with very low user interaction during long-term operation. TSI has continually built expertise since releasing the first commercially available CPC in 1979.
Adding insight on particle size
Using a CPC as the basis, adding sizing capability adds another level of insight. Since airborne particles are present over a very wide size range, various technologies have been developed to measure particle diameter. Ultrafine particles can be measured with high time and size resolution, typically covering a particle size range between 1 nm and 1 μm. These ultrafine particle spectrometers are based on electrical mobility measurement (as described in ISO15900:2009) and utilise CPCs to count the number of particles in each size channel. Determining the ultrafine particle size distribution is described in the new European standard draft CEN/TS 17434 as released in 2019. In this standard, the method ‘Mobility Particle Size Spectrometer (MPSS)’ is used to cover a size range from 10 nm to 800 nm. TSI’s Scanning Mobility Particle Sizer (SMPS) fits this need, and has been making ambient air measurements worldwide for years.
Select your solution
TSI is the most trusted provider of Condensation Particle Counters and Mobility Particle Size Spectrometers (SMPS, MPSS) in the world. The instruments are available in various versions, to cover applications such as new particle formations (down to 1 nm), engine emission measurements, and also ambient monitoring. In the context of developing regulations and evolving science, TSI will continue to serve the ambient monitoring community for years to come.
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