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Particulate matter
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
The condensation particle counter (CPC, also known as the condensation nucleus counter (CNC) or Aitken nucleus counter) is used to measure the total number concentration of particles in the diameter range from a few nanometres to 1 μm. The particles are introduced into a chamber where they are exposed to a water- or alcohol-based supersaturated vapour. The particles act as condensation nuclei for droplets that grow to around 10 μm diameter, when they are large enough to be detected and counted, usually by optical methods. As the growth is diffusion-limited, all the droplets are of similar diameter even if the original particles were highly polydisperse. Because the supersaturation is very high, it makes no difference what the original particle was made of – it simply serves as a condensation centre. In some designs the supersaturation is created cyclically by adiabatic expansion, and in some it is created continuously by conduction cooling. Individual particles can be counted if the concentration is low enough. At higher concentrations an optical method based on attenuation of a beam by the droplet cloud is used. Problems may be caused by excessive concentrations of nanoparticles (<20 nm), which are undercounted because the vapour has been depleted. An adaptation of this technique is used to count cloud condensation nuclei (CCN) particles. These are activated by the low supersaturations (0.01%–1%) found in updrafts and clouds. The controlled supersaturation is achieved by maintaining two wetted surfaces at different temperatures.
Managing Risks in Occupational Environments
Published in Jo Anne Shatkin, Nanotechnology, 2017
The limitations of respirable samplers have made direct-reading instruments more attractive for evaluating exposures to engineered nanomaterials. Table 8.1 shows images of some direct-reading instruments used in monitoring of engineered nanomaterials in the workplace. Two instruments in particular have been consistently recommended for this purpose: the condensation particle counter (CPC), which measures particles from about 10 nm to 1000 nm; and the optical particle counter (OPC), which measures particles from 300 nm to roughly 10 μm (Table 8.1A). These instruments can be used to estimate ultrafine particle number and respirable mass concentrations (Peters et al. 2006; NIOSH 2009). This information is valuable because it enables large and small particles to be “seen” by the EHS professional and can be used to identify areas where controls are needed and to evaluate their effectiveness once installed. They are, however, limited to area measurements because of their size.
Measurement of gases and particles
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
The condensation particle counter (CPC, also known as the condensation nucleus counter (CNC) or Aitken nucleus counter) is used to measure the total number concentration of particles in the diameter range from a few nanometres to 1 μm. The particles are introduced into a chamber where they are exposed to a water-or alcohol-based supersaturated vapour. The particles act as condensation nuclei for droplets that grow to around 10 μm diameter, when they are large enough to be detected and counted, usually by optical methods. Since the growth is diffusion-limited, all the droplets are of similar diameter even if the original particles were highly polydisperse. Because the supersaturation is very high, it makes no difference what the original particle was made of – it simply serves as a condensation centre. In some designs the supersaturation is created cyclically by adiabatic expansion, and in some it is created continuously by conduction cooling. Individual particles can be counted if the concentration is low enough. At higher concentrations an optical method based on attenuation of a beam by the droplet cloud is used. Problems may be caused by excessive concentrations of nanoparticles (<20 nm), which are undercounted because the vapour has been depleted. An adaptation of this technique is used to count cloud CCN particles. These are activated by the low supersatu-rations (0.01–1%) found in updrafts and clouds. The controlled supersaturation is achieved by maintaining two wetted surfaces at different temperatures.
Development of a two-column particle sizer (TC-PS) for simultaneous measurements of particle concentration and size distribution
Published in Aerosol Science and Technology, 2023
Handol Lee, Woo Young Kim, Dong-Bin Kwak, Kang-Ho Ahn
The most widely used instrument to measure the number concentrations of submicron particles (down to a few nanometers in size) is a condensation particle counter (CPC). In a CPC, optically undetectable small particles are exposed to supersaturated vapor, which condenses on the particle surfaces. Consequently, these small particles grow larger and become detectable by light scattering. The original work on the development of CPC goes back to more than a century ago, and it was developed by John Aitken in 1888 (McMurry 2000). Since then, many researchers have worked on CPCs theoretically and experimentally (Barmpounis et al. 2018; Iida et al. 2008, Iida, Stolzenburg, and McMurry 2009; Han et al. 2008; Hering et al. 2005; Ahn and Liu 1990a, 1990b). In other works, the performance evaluation or advancement of commercially available CPCs have been conducted (Picard, Attoui, and Sellegri 2019; Bau et al. 2017; Hermann et al. 2007; Petäjä et al. 2006; Kesten, Reineking, and Porstendörfer 1991).
Review of sub-3 nm condensation particle counters, calibrations, and cluster generation methods
Published in Aerosol Science and Technology, 2019
Juha Kangasluoma, Michael Attoui
In gas-to-particle conversion vapors undergo chemical reactions and clustering, producing molecular clusters that grow to larger sizes via vapor condensation and coagulation. Such a process takes place in the atmosphere, and in many industrial and nanomaterial synthesis processes (Ahonen et al. 2017; Alanen et al. 2015; Cai et al. 2017b; Carbone, Attoui, and Gomez 2016; Feng et al. 2016; Hietikko et al. 2018; Jiang et al. 2011c; Kangasluoma et al. 2015b; Kirkby et al. 2011, 2016; Kuang et al. 2012a; Kulmala et al. 2013; Maisser et al. 2015a; Nosko, Vanhanen and Olofsson 2017; Rönkkö et al. 2017; Wagner et al. 2017; Wang et al. 2017a). The need to understand and quantify these processes starting from the smallest molecular clusters has led to the development of several particle counting instruments and methods to verify their operation. Electrical methods are used in some cases to count the sub-3 nm particles, while a condensation particle counter (CPC) is the most commonly used detector due to its extremely low background noise levels. In this review, we focus on the CPCs capable for sub-3 nm particle counting and the preceding developments, the CPC calibrations and cluster production methods for the calibrations.
Experimental verification of principal losses in a regulatory particulate matter emissions sampling system for aircraft turbine engines
Published in Aerosol Science and Technology, 2021
D. B. Kittelson, J. Swanson, M. Aldridge, R. A. Giannelli, J. S. Kinsey, J. A. Stevens, D. S. Liscinsky, D. Hagen, C. Leggett, K. Stephens, B. Hoffman, R. Howard, R. W. Frazee, W. Silvis, T. McArthur, P. Lobo, S. Achterberg, M. Trueblood, K. Thomson, L. Wolff, K. Cerully, T. Onasch, R. Miake-Lye, A. Freedman, W. Bachalo, G. Payne
Table 1 lists the sections of the sampling system and the loss mechanisms, i.e., thermophoretic, diffusional, and impaction (e.g., due to bends), that can occur for each section. The first part of the sampling system, Section 1 in Figure 1, is a sampling probe which is not temperature controlled located at the exit plane of the engine. From the probe, the sample flows through a heated (160 °C) sample line (up to 8 meters in length including the probe) to a three-way splitter (splitter1) also heated to 160 °C. In Section 2 of the sampling system, the splitter supplies sample for gaseous (total hydrocarbons, NOx, CO, CO2) emissions measurements, nvPM emissions measurement, and a third line to remove excess flow through the pressure control valve during periods of high thrust. From the splitter1 outlet the nvPM sample flows to an ejector diluter located within one meter of the splitter1 inlet which is also heated to 160 °C. During dilution, there is a sample temperature change from 160 °C to 60 °C which is mainly executed through the temperature controlled (60 °C) dilutor and N2 dilution gas. From the diluter outlet the nvPM sample flows at 25 ± 2 liters per minute (lpm) through the temperature controlled (60 °C) 25-meter line in Section 3 to a second splitter which provides sample to the number instrument, the mass instrument, and a third line for excess flow and the measurement of CO2. The sampling system components from the diluter outlet to the mass and number instrument inlets are all heated to 60 °C. The number instrument consists of a few short sample lines, a diluter, a volatile particle remover, and a condensation particle counter (CPC).