Recent experiments of the working group on ultrafine aerosols — the 1979 wufa workshop (original) (raw)
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Intercomparison of different “absolute” instruments for measurement of aerosol number concentration
Journal of Aerosol Science, 1982
During the 1979 workshop of the working group on ultrafine aerosols (WUFA) an intercomparison of different instruments for measurement of aerosol number concentrations was performed. Each of these instruments (TSl-aerosol electrometer, TSI-condensation nuclei counter, Jaenicke-condensation nuclei counter, size analyzing nuclei counter SANC) can be regarded as "absolute", because they do not depend on empirical calibration relative to external reference standards. Number concentrations were measured for monodispersed NaCl-aerosols with a mean particle diameter of 56 nm, generated by means of a collision atomizer and an electrostatic aerosol classifier. The transmission losses in the SANCohumidifier were determined quantitatively and the SANC-measurements were properly corrected. Measurements were performed over a concentration range from about 2.5 x 102 to 3.5 x 105 cm -3. Considering the differences between the various applied measuring techniques, fair agreement of the obtained concentration data was observed. The TSl-condensation nuclei counter agrees closely with the TSI-aerosol electrometer, however, it can be regarded as an "absolute" instrument only for concentrations below 103 cm-3. For low concentrations the Jaenicke-condensation nuclei counter tends to agree with the average concentration, obtained from all instruments used, above 104 cm-3 it agrees closely with the SANC. The readings of TSI-aerosol electrometer and SANC are quite linearly related over the whole concentration range, the SANC being low by a factor of about 0.59. Thus different measuring techniques, based on completely different principles, yield comparable aerosol number concentrations and accordingly condensation nuclei counters are truly aerosol counters.
Measurement of Ultrafine Particles: A Comparison of Two Handheld Condensation Particle Counters
Aerosol Science and Technology, 2004
The objective of this study was to compare two real-time condensation particle counters for measurement of number concentrations of ultrafine particles (UFPs). The comparison is based on the data from side-by-side measurements conducted in several locations, both indoors and outdoors. CPC 3007 and P-Trak TM 8525 manufactured by TSI (instruments A and B, respectively) were used simultaneously. They measure particles in sizes from 0.01 to greater than 1 µm and 0.02 to greater than 1 µm, respectively. The results reveal a good correlation between the two instruments. The ratios of measured aerosol concentrations varied from 0.81 to 1.17, which implies that in all data sets the difference between the two instruments was less than ±20%. About 63% of the results were in the range of ±10%, and about 44% showed differences less than ±5%. The maximum particle concentration detected by instrument A was approximately 105,000 particles cm −3 and the minimum was about 230 particles cm −3 . Because of the lower particle size threshold for instrument A, it was expected that this instrument should never show concentrations lower than those detected by instrument B. This was the case in most of the measurement series. The results revealed that the concentration of UFPs changes rapidly, especially in the presence of a local UFP source. A sampling interval of 1 min is sufficient to provide substantial information about the change in concentration level.
An Ultrafine, Water-Based Condensation Particle Counter and its Evaluation under Field Conditions
Aerosol Science and Technology, 2008
An ultrafine, water-based condensation particle counter (U-WCPC, TSI Model 3786) has been compared to a butanol-based ultrafine counter (U-BCPC, TSI Model 3025) for measurement of atmospheric and freeway-tunnel aerosols. The U-WCPC utilizes a warm, wet-walled growth tube to activate and grow particles through water condensation in a laminar-flow. It has an aerosol sampling rate of 0.3 L/min, and a nominal detection limit near 3 nm. Several field comparisons were made to the butanol-based instrument with the same nominal detection limit. For measurements of size-selected aerosols with diameters of 5 nm and larger the two instruments generally agreed, with a mean response within 5%. At 3 nm particle size differences were observed, and these differences varied with the data set. Measurements of ambient aerosol in Boulder, Colorado showed higher counting efficiency at 3 nm with the U-BCPC, while in a California freeway tunnel the opposite trend was observed, with higher counting efficiencies at 3 nm observed by the U-WCPC. For direct measurement of atmospheric aerosols, the two types of instruments yielded equivalent concentrations, independent of particle number concentration.
Particle size dependent response of aerosol counters
Atmospheric Research, 2002
During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions. The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the 0169-8095/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 -8 0 9 5 ( 0 2 ) 0 0 0 11 -X $ Coordinated within the Committee on Nucleation and Atmospheric Aerosols, International Commission on Clouds and Precipitation, IAMAS-IUGG.
Calibration of a Condensation Particle Counter Using a NIST Traceable Method
Aerosol Science and Technology, 2009
This work presents a calibration of a commercial condensation particle counter using National Institute of Standards and Technology (NIST) traceable methods. By the nature of the metrology involved, this work also compares the measurement results of three independent techniques for measuring aerosol concentration: continuous flow condensation particle counter (CPC); aerosol electrometer (AE); and the aerosol concentration derived from microscopic particle counting. Because of the transient nature of aerosol, there are no concentration artifact standards such as exist for particle diameter standards. We employ a mobility classifier to produce a nearly monodisperse, 80 nm, polystyrene latex aerosol. The test aerosol is used as a challenge for the CPC and the AE, and is subsequently filter sampled for electron microscopy. Our test stand design incorporates a continuous CPC aerosol concentration monitor to verify the aerosol stability. The CPC determines particle concentration by single particle counting at a constant sample flow rate. The AE has been calibrated to a NIST traceable current standard. The subsequent aerosol concentration measurement is obtained by determining the electrical current produced by a charged aerosol transported to the detector by a controlled aerosol flow rate. We have NIST traceability for flow rates for all methods and a methodology to calibrate the AE to NIST traceable electrical standards. The latter provides a calibration and a determination of the uncertainty in the aerosol derived current measurement. A bias in the measurements due to multiple charged particles was observed and overcome by using an electrospray aerosol generator to produce the challenge particles. This generator was able to produce aerosol concentrations over the range of 100 particles/cm 3 to 15 000 particles/cm 3 with lower number of
International Journal of Nanoparticles, 2008
The accurate measurement of ultrafine and submicron sized airborne particles is a challenging task. Since several studies have linked exposures to airborne ultrafine particles to elevated human health risks, the need to assess the concentrations of particles in the workplace that are below one micron in diameter is imperative. Several techniques for directly monitoring micro and nanoparticles are available and others are being tested for their merit. Condensation Nuclei Counters (CNCs), portable condensation particle counters, differential mobility analysers, electron microscopy and other novel approaches to measuring micro and nanoparticles have been employed in investigations. The purpose of this paper is to elucidate the results from three studies involving the measurement of airborne particles with a laser particle counter and condensation nuclei counter. The three environments include: a gambling casino, a Shielded Metal Arc Welding (SMAW) operation and a general manufacturing facility with welding, cutting and grinding operations being performed.
A Wide-Range Particle Spectrometer for Aerosol Measurement from 0.010 µm to 10 µm
Aerosol and Air Quality Research, 2010
The Wide-range Particle Spectrometer (WPS™) is a recently introduced commercial instrument with the unique capability to measure size distributions of aerosols from 0.01 to 10 µm in diameter. The instrument includes a Scanning Mobility Spectrometer (SMS) comprised of a Differential Mobility Analyzer (DMA) and a Condensation Particle Counter (CPC) for particle measurement from 0.01 to 0.5 µm and a Laser Particle Spectrometer (LPS) for measurement in the ~0.4 to 10 µm range. These components are small enough to fit into a small portable cabinet (~26 kg) with all accompanying control hardware and electronics. No external pumps are required and power consumption is only about 150 W. The DMA is calibrated with Standard Reference Materials (SRM) from the U.S. National Institute of Standards and Technology (NIST), including SRM 1691 and SRM 1963a. These are uniform size polystyrene latex (PSL) spheres available from NIST with mean diameters of 0.269 µm and 0.1018 µm respectively. The CPC has a dual reservoir design to prevent the working fluid from being contaminated by water due to moisture condensation in the condenser. The LPS is calibrated with four NIST-traceable PSL sphere sizes. Calibration curves are generated not only for PSL (real refractive index of 1.585), but also for discrete values real refractive index ranging from 1.30 to 1.60. This procedure allows the user to select the most appropriate curve for determination of the light-scattering-equivalent sphere size that takes into account the effect due to refractive index of real aerosols. The LPS has a wide-angle collection optics design to produce a monotonic response curve for routine measurement in the field.
Ultrafine Aerosol Measurement Using a Condensation Nucleus Counter with Pulse Height Analysis
Aerosol Science and Technology, 1996
Photodetector pulse heights from an ultrafine condensation nucleus counter increase monotonically with particle size in the-2.7-15 nm diameter range. This relationship can be used to measure concentrations and size distributions of ultrafine aerosols. In this study, we investigated the sensitivity of size-dependent pulse heights to total particle concentration, absolute pressure (0.25-1 atmosphere), and particle composition (H2S04, (NH,),SO,,NaCl, and tungsten oxide). We found that pulse heights shifted significantly with pressure and slightly with concentration. Coincidence led to errors for concentrations exceeding 4 X lo3 ~m-~. Over the range of conditions investigated, however, the observed shifts in the pulse height voltage were independent of size. The pulse height method is particularly applicable to situations involving low ultrafine particle concentrations, such as are encountered in the remote troposphere.
Journal of Physics: Conference Series
This study aim is to compare the number concentration of airborne nanoparticles reported by 13 different Condensation Particle Counters (CPC) with regards to a reference CPC, for a set of aerosols of interest. Among the models investigated, 5 are handheld CPC, while the 8 others are stationary CPC. The latter include butanol-based CPC as well as water-based CPC. Polydisperse test aerosols with modal diameters between 6 and 460 nm were produced in the CAIMAN experimental facility. Non-hydrophobic aerosols consisted of metal-based particles (Ti, C, Al, Cu, Ag), as well as nebulized suspensions (SiO2). Hydrophobic particles consisted of DEHS as well as alkanes (n-C13 to n-C20). Overall, about 400 different conditions were investigated to represent a wide range of aerosols potentially encountered in workplaces. The range of number concentrations provided by the reference CPC was 500 – 400 000 cm−3. To highlight the possible effect of particle counting efficiency on the total concentrati...