The Use of STIM and PESA to Measure Profiles of Aerosol Mass and Hydrogen Content,Respectively, across Mylar Rotating Drums Impactor Samples

A method has been developed for measuring profiles of aerosol mass on thin (480 w g/cm 2 ) Apiezon-L coated Mylar films employed in rotating drum aerosol impactor samplers using the ion beam analysis technique scanning transmission ion microscopy (STIM). The greased Mylar films are excellent impaction substrates and possess excellent uniformity in projected density, making them an ideal substrate for STIM analysis. The uniformity in projected density of a film enables STIM with a 3 MeV proton beam to produce profiles of aerosol mass with an accuracy of better than 90% and a mass sensitivity approaching 10 w g/cm 2 . Further, we have extended proton elastic scattering analysis (PESA) to the same films, achieving measurement of an organic surrogate. Although the films contain ～ 20 w g/cm 2 hydrogen, the spatial uniformity in film hydrogen content enables PESA with a 3 MeV proton beam to produce profiles of hydrogen arising solely from the aerosols with an accuracy to within - 1 w g/cm 2 and a mass sensitivity of ～ 1 w g/cm 2 . These measurements when combined with synchrotron-x-ray fluorescence (S-XRF) measurements on the same film allow mass closure, sum of species versus measured mass, a key quality assurance protocol, to be approached. All 3 techniques were applied to very fine and ultra-fine particles collected in Fresno, CA, November, 2000 by slotted DRUM samplers. Temporal resolution in the resulting profiles was h 6 h. The dramatic changes in composition versus size and time, and new types of elemental correlations unseen in PM 2.5 filters, will be major assets in correlating aerosols and health impacts, visibility degradation, and the effects of aerosols on climate.     

Measuring the Mass Extinction Efficiency of Elemental Carbon in Rural Aerosol

Previous measurements of the mass absorption efficiency of ambient elemental carbon (EC) indicate that EC optical properties vary with location and imply that the variations may be due to different particle size distributions and composition at different locations (Liousse et al. 1993). For this reason, optical properties appropriate to regional characteristics of EC, determined over the wavelengths of light significant for aerosol extinction, are needed to adequately model the radiative impact of this species. Here we present a method for measuring one of these properties, the mass extinction efficiency (m 2 g -1 ) of EC, as a function of particle size and wavelength of light. In this method, size segregated atmospheric aerosol particles are collected on Nucleopore filters. The filter samples are extracted in a mixture of 30% isopropanol and 70% deionized distilled water to form a suspension of insoluble EC particles. Transmission of light through the extraction liquid is measured over wavelengths from 300 to 800 nm using a spectrophotometer. The transmission measurements taken through the liquid extract are mathematically converted to EC extinction coefficients in air. Although the conversion is a function of a parameter determined from Mie theory, which assumes monodisperse, spherical particles with a known density and refractive index relative to the medium, the method is shown to be reasonably insensitive to these assumptions. Using EC mass concentration obtained from a parallel sample, the EC mass extinction efficiency (in air) is calculated from the extinction coefficient (in air). This method is applied to a rural Midwestern, midcontinental aerosol. In general, the EC mass extinction efficiency in air is highest at lower wavelengths and for smaller particles. For particles with diameters between 0.09 and 2.7 w m and an assumed density of 1.9 g cm -3 , the measured EC mass extinction efficiency at 550 nm ranges from 7.3 to 1.7 m 2 g -1 .     

The ratio of the extinction coefficient to the mass of atmospheric aerosol particles as a function of the relative humidity

The ratio R_K of the extinction coefficient of aerosol particles in cm ¹, at the wavelength of light λ = 0·55 μm, and the mass of atmospheric aerosol particles in gem³ has been computed as function of the relative humidity for six types of continental and maritime aerosols. With the mean value R_K = 10⁴ cm²/g for all aerosol types being assumed to be independent of relative humidity, only the order of magnitude of the aerosol mass can be determined from visibility observation or measurement of the extinction coefficient of the aerosol particles.     

Development of a PM 10/PM 2.5 Cascade Impactor and In-Stack Measurements

Combustion and industrial processes are an important source of particles. Due to the new PM 10 and PM 2.5 standards for ambient air quality, a sampling system for PM 10/PM 2.5 in-stack measurements was designed and calibrated. In this new system, the exhaust gas is isokinetically sucked into a two stage impactor through the inlet of a plane filter device and the aerosol is fractionated in the particle size classes >10 w m, 10-2.5 w m, and <2.5 w m. Due to a relatively high volume flow (ca. 3.2 m 3 /h, depending on exhaust gas conditions), sampling times are kept short, e.g., 30 min for dust concentrations of 10 mg/m 3 . The impactor was calibrated in the laboratory and then operated at various industrial plants. Parallel measurements with identical devices showed average standard deviations of 3.1% (PM 10) and 3.4% (PM 2.5). Measurements of the cascade impactor together with the plane filter device gave plausible results and average PMx/TSP ratios of 0.49 (PM 2.5/TSP) and 0.78 (PM 10/TSP), showing a large variability for different processes. Elemental analysis using total-reflection X-ray fluorescence spectrometry, together with the size-fractionated sampling, proved to give characteristic patterns of the emitted aerosols, which can be used for a subsequent fingerprint modelling for source apportionment of ambient air pollution.     

Albedo Measurements and Optical Sizing of Single Aerosol Particles

Aerosols play an important role in global climate change by their interactions with incoming solar radiation and outgoing longwave radiation from the planetary surface. The climate effects of aerosols depend on their scattering and absorption properties. This article describes the development of an instrument (ASTER: Aerosol Scattering To Extinction Ratio) that simultaneously measures the scattering and extinction of single aerosol particles. ASTER uses a high-Q cavity to amplify the extinction signal and innovative optics to collect the scattered light. It can distinguish many partially absorbing particles from a few black ones even if the bulk absorption is the same. Optical sizing and single-scattering albedo measurements were made for laboratory-generated particles with diameters from about 300 nanometers to above one micrometer. Using this prototype instrument, changes in albedo for single particles of 20% or greater were detected by measurement of the scattering and extinction. Optical sizing of the individual particles to within ～ 50 nm was accomplished using the ratio of the forward scattered light to the total scattering. Initial measurements of laboratory air showed a mode of highly absorbing particles. This article reports design and early laboratory tests on ASTER.     

Real-Time Characterization of the Composition of Individual Particles Emitted From Ultrafine Particle Concentrators

Particle concentrators are commonly used for controlling exposure levels to ambient ultrafine, fine, and coarse aerosols over a broad range of concentrations. For ultrafine aerosols, these concentrators require water condensation technology to grow and enrich these smaller sized particles (D _a < 100 nm). Because the chemistry of the particles is directly related to their toxicity, any changes induced by ultrafine concentrators on ambient particles need to be better characterized in order to fully understand the results obtained in health exposure studies. Using aerosol time-of-flight mass spectrometry (ATOFMS), the size-resolved chemistry was measured of concentrated ultrafine and accumulation mode (50–300 nm) particles from several particle concentrators with different designs. This is the first report detailing the size-resolved distributions of elemental carbon (EC) and organic carbon (OC) particles sampled from concentrators. Experimental measurements of the single particle mixing state of particles in concentrated versus non-concentrated ambient air show transformations of ultrafine EC particles occur as they become coated with organic carbon (OC) species during the concentration process. Based on relative ion intensities, concentrated ultrafine particles showed a 30% increase in the amount of OC on the EC particles for the same aerodynamic size. An increase in the number fraction of aromatic- and polycyclic aromatic hydrocarbon-containing particles was also observed in both the ultrafine and fine size modes. The most likely explanation for such changes is gas-to-particle partitioning of organic components (e.g., water-soluble organic compounds) from the high volume of air used in the concentrator into aqueous phase ultrafine and fine aqueous particles created during the particle enrichment process.     

Automated Measurement of the Size and Concentration of Airborne Particulate Nitrate

A three-stage, cascaded integrated collection and vaporization system has been developed to provide automated, 10 min resolution monitoring of the size and concentration of fine particulate nitrate in the atmosphere. Particles are collected (7 min) by a humidified impaction process, and analyzed in place (3 min) by flash vaporization and chemiluminescent detection of the evolved nitrogen oxides. The three size fractions, < 0.45 w m, 0.45-1.0 w m, and 1.0-2.5 w m, are chosen to distinguish the condensation, droplet, and coarse components of PM 2.5 . The size precut at 2.5 w m is done at ambient conditions, while the size fractionation at 1.0 w m and 0.45 w m is done at a constant relative humidity of 65%. The system is calibrated with laboratory aerosols, including comparison of sizing for hygroscopic salt and hydrophobic organic aerosols. The complete system is tested with monodisperse ammonium nitrate aerosol generated with a high-flow differential mobility analyzer coupled with an impactor precut and yields results consistent with the calibration of the individual stages.     

Scattering and absorption coefficients vs. chemical composition of fine atmospheric aerosol particles under regional conditions in Hungary

The light scattering and absorption coefficients of aerosol particles with a dry diameter below 1 μm were recorded in the country air of Hungary. Concentrations of different inorganic and organic ions were measured in parallel to estimate the nature of particles causing light scattering. The sample air was heated gently to maintain a relative humidity of 30% and coarse particles were removed by a multi-jet impactor. The aerosol light scattering coefficient was monitored with an integrating nephelometer, while absorption was measured on the basis of the rate of blackening of a filter. Results gained during two time periods, mostly in the winter months, are presented in this paper. Data show that the winter average light scattering coefficient is 93 Mm⁻¹, while the corresponding figure for light absorption is 8.9 Mm⁻¹. This results in a single-scatter albedo of 0.91. Comparison of the optical data with chemical information indicates that there is a good correlation between light scattering coefficient and sulfate concentration. The relationship is significant, in particular, in the winter half-year. Regression calculations among the measured parameters suggest for summer and winter half-year a sulfate mass scattering efficiency of 6 and 8 m² g⁻¹, respectively. By using a mass absorption efficiency of 10 m² g⁻¹, the average winter absorption coefficient corresponds to an elemental carbon concentration of 0.9 μg m⁻³.     

Evaluation of Elemental and Black Carbon Measurements from the GAViM and IMPROVE Networks

The GAViM program provides fine particulate and visibility data for several remote locations in Canada. Two long-term intercomparison studies between the GAViM and a major U.S. aerosol monitoring network, IMPROVE, were used to evaluate the uncertainty in the analytical data produced by proton induced x-ray emission (PIXE), proton elastic scattering analysis (PESA), and gravimetric analysis. GAViM and IMPROVE agreed well for elements from Fe to Zn where PIXE is the most sensitive; the relative difference between the 2 networks for Fe and Zn was <2%. Some lighter elements, e.g., sodium or sulphur, revealed a difference of 10-20%. Furthermore, an empiric conversion scheme for the GAViM absorption data produced by the laser integrated plate method (LIPM) was derived from the comparison to the IMPROVE thermal/optical reflectance (TOR) data. This conversion depends on the aerosol composition and is therefore site specific. It allows estimation of the elemental carbon concentrations from the historic raw light absorption values obtained by LIPM. If the mass attenuation coefficient of the fine aerosol collected at the 2 remote GAViM sites is assumed to be equal to 10 m 2 /g, then the results imply that the light absorption coefficient measured by LIPM is generally higher than the true value by up to a factor of 1.3 or 1.8, respectively. In both cases, LIPM overestimated the black carbon content, mostly for the lightly loaded samples.     

Photothermal Interferometric Aerosol Absorption Spectrometry

Aerosol light absorption still remains a difficult quantity to measure at the precision, accuracy and temporal resolution necessary to quantitatively bound the contribution of this direct effect on aerosol radiative forcing. These continuing difficulties are due, in part, because aerosol extinction is dominated by light scattering. In response to these and other issues, the aerosol community has been developing a new generation of instrumentation that can measure aerosol absorption without the need to deposit aerosols on a filter. Here we introduce work on the application of photothermal interferometry (PTI) towards this measurement problem. The advantages of this approach are: its complete insensitivity to aerosol scattering (true for any photothermal technique) and high sensitivity resulting from use of an interferometric technique. Using NO₂ as a calibration standard, the accuracy of the PTI technique was measured to be 5% (95% confidence interval). Measurement at a 10-second time constant yields a precision of 0.2 Mm^?1 (95% confidence interval) and a lower limit of detection of 0.4 Mm^?1 for a sample pathlength of 5 cm. Using laboratory-generated nigrosin aerosols an intercomparison between the PTI and a 3-λ Particle Soot Absorption Photometer (PSAP) gives a slope of 0.96 ± 0.02. Acquisition of absorption coefficients for ambient aerosols reveals very good agreement between the two instruments except for periods of high relative humidity (>70%) whereupon the PSAP reports a larger absorption coefficient.     

Combustion Generated Nickel Species Aerosols: Role of Chemical and Physical Properties on Lung Injury

Systematic manipulation of furnace temperature, residence time, and dilution air was used to study the formation of submicrometer nickel oxide (NiO) or nickel sulfate hexahydrate (NiSO 4 ) particles in a horizontal, laminar flow tube reactor. Chemical speciation, morphological changes, and aerosol size distributions were measured using x-ray diffraction, transmission electron microscopy, and diffusion mobility analysis, respectively. A technique was developed to use these submicrometer nickel species aerosols in animal inhalation studies. Representative aerosols were administered to C57BL/6J mice by intratracheal instillation or whole-body inhalation to study the effect of submicrometer particles on pulmonary injury. For instillation, NiO particles having a geometric mass mean diameter ( d pg ) of 40, 300, and 1000 nm were generated by pyrolysis of nickel nitrate hexahydrate aerosol suspended in physiological saline and administered at a dose corresponding to 3, 30, 300, or 3000 w g Ni/kg body weight. Bronchoalveolar lavage fluid was collected 18 hr after instillation and analyzed for total and differential cell counts, cell viability, and total protein. For inhalation experiments, an acute, whole-body exposure was conducted, exposing mice to 6, 24, 48, or 72 hr of continuous submicrometer NiO aerosol ( d pg = 50 nm; 340 w g Ni/m 3 ) or 24, 48, or 72 hr of NiSO 4 aerosol ( d pg = 60 nm; 420 w g Ni/m 3 ; d pg = 250 nm; 480 w g Ni/m 3 ). Exposure to NiO produced no significant lung injury when either instilled or inhaled, whereas inhaled NiSO 4 caused significant increases in protein content and neutrophil count in lavage following 48 or 72 hr of exposure. These findings suggest that submicrometer NiSO4 aerosols generated in combustion processes are more acutely injurious to the lung than an equivalent mass of NiO aerosol.     

A portable,four-wavelength,single-cell photoacoustic spectrometer for ambient aerosol absorption

Aerosols directly affect Earth's climate by scattering and absorbing solar radiation. Although they are ubiquitous in Earth's atmosphere, direct, in situ, wavelength-resolved measurements of aerosol optical properties remain challenging. As a result, the so-called aerosol direct effects are one of the largest uncertainties in predictions of Earth's future climate, and new instrumentation is needed to provide measurements of the absorption of sunlight by atmospheric particles. We have developed a portable, four-wavelength, single-cell photoacoustic spectrometer for simultaneous measurement of aerosol absorption at 406, 532, 662, and 785 nm, with an additional extinction measurement at 662 nm via a built-in cavity ringdown spectrometer. The instrument, dubbed MultiPAS-IV, is compact, robust, has low power requirements, and utilizes a multipass optical arrangement to achieve typical detection limits of 0.6–0.7 Mm^?1 for absorption (2σ, 2-min average). Tests with nigrosin aerosols show agreement with Mie theory calculations to within 2%, and comparison with a 7-wavelength aethalometer shows good correlation for ambient (Athens, GA, USA) aerosols. We demonstrate the utility of the broad spectral coverage and sensitivity of the MultiPAS-IV for calculating the absorption Ångström exponent of black carbon (AAE_BC, median value of 0.70) in ambient aerosols and use this value to derive the brown carbon contributions to absorption at 406 nm (43%) and 532 nm (13%) and its wavelength dependence (AAE_BrC = 6.3).

Copyright © 2018 American Association for Aerosol Research     

Generation of high concentrations of respirable solid-phase aerosols from viscous fluids

High outputs of respirable solid-phase aerosols were generated from viscous solutions or suspensions of low- and high-molecular weight polyvinylpyrrolidone (PVP) solutions, 10% (w/v) albumin and, gamma globulin solutions as well as 10.3% (w/v) surfactant suspensions. A central fluid flow was aerosolized by coaxial converging compressed air. The water was evaporated from the droplets using warm dilution air and infrared radiation. The resulting aerosol particles were concentrated using a virtual impactor. The aerosols were generated at fluid flow rates between 1 and 3?ml/min and delivered at a flow rate of 44?l/min as 2.6–3.6?μm MMAD aerosols with geometric standard deviations between 1.5 and 2. Increases in viscosity over the range of 4–39 cSt caused a modest increase in MMAD. Increases in aerosol exit orifice diameter were associated with a decrease in aerosol diameter. Increases in compressed air pressure caused a decrease in aerosol diameter. Increases in fluid flow rate resulted in modest increases in MMAD together with proportional increases in output mass. Aerosolizing 10% 8?kDa PVP at 3?ml/min resulted in the delivery of 193?mg/min of PVP at 64% efficiency enabling 1.2?g to be collected in 7?min. Aerosolizing 10.3% surfactant suspensions at 3?ml/min resulted in the delivery of up to 163?mg/min with 59% efficiency. The surface tension of the surfactant was not changed by these processes. SEM showed dimpled particles of PVP, albumin, and gamma globulin indicating that their aerodynamic diameter was less than their morphometric diameter.

Copyright © 2018 American Association for Aerosol Research     

System design and test method for measuring respirator filter efficiency using mycobacterium aerosols

Recently, the protection of health care workers from tuberculosis-containing aerosols has been the subject of considerable debate. An experimental apparatus and test protocol were developed to measure the collection efficiency of surgical mask and respirator filter media using a microbial aerosol challenge. Mycobacterium chelonae (M. chelonae), used as a surrogate for Mycobacterium tuberculosis, was generated from liquid suspension using a Collison nebulizer. Upstream and downstream concentrations of viable aerosol particles were measured using Andersen cascade impactors, while total particle concentrations were measured with an aerodynamic particle sizer (APS). A monodisperse polystyrene latex (PSL) sphere aerosol (0.804 μm) was used in separate experiments to measure filter efficiency; concentrations were determined with the APS. The mycobacterial aerosol ranged in size from 0.65 to 2.2 μm when measured with the cascade impactor. A similar size range was found with the APS, yielding a count median diameter of about 0.8 μm. Samples of the mycobacterial aerosol were collected on glass slides, stained M. chelonae, as determined by environmental scanning electron microscope, were found to be rod shaped with an average length of 2 μm and average width of 0.3 μm. To evaluate the apparatus over a range of filter efficiencies (10–100%), different layers of fiberglass filter paper were tested for penetration using a 0.12 μm dioctyl phthalate (DOP) aerosol measured with a light scattering photometer, in addition to the mycobacterial and PSL aerosols. For the range of efficiencies tested it was shown that filter collection of DOP was linearly related to that of both mycobacterial and PSL sphere aerosols (r² = 0.99), demonstrating that an inert aerosol may be used to predict the collection of biological aerosols by such filter media.     

Calibration and Intercomparison of Filter-Based Measurements of Visible Light Absorption by Aerosols

Data on light absorption by atmospheric particles are scarce relative to the need for global characterization. Most of the existing data come from methods that measure the change in light transmission through a filter on which particles are collected. We present a calibration of a recently developed filter-based instrument for continuous measurement of light absorption (model PSAP, Radiance Research, Seattle, WA) that has been incorporated in several measurement programs. This calibration uses a reference absorption determined as the difference between light extinction and light scattering by unaltered (suspended) particles. In addition, we perform the same calibration for two other common filter-based methods: an Integrating Plate and the Hybrid Integrating Plate System. For each method, we assess the responses to both particulate light scattering and particulate light absorption. We find that each of the instruments exhibits a significant response to nonabsorbing aerosols and overestimates absorption at 550 nm by suspended particles by about 20-30%. We also present correction factors for the use of the PSAP.     

Spatio-temporal variability in atmospheric abundances of EC,OC and WSOC over Northern India

The atmospheric abundances of elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC) have been measured in aerosol samples collected during wintertime (December–March) from selected sites (urban, rural and high-altitude) in northern India. A characteristic feature of their abundance pattern, at urban sites, is reflected in the OC/EC ratios (range: 2.4–14.5, Av=7.8±2.4, n=77) indicating dominant contribution from biomass burning sources (wood-fuel and agriculture waste). This is in sharp contrast to the OC/EC ratios at a rural site (range: 2.1–4.0, Av=3.1±0.6, n=7) influenced by emissions from coal-fired industries. The long-term measurements made from a high-altitude site (～2000 m amsl) reveal significantly lower abundances of EC and OC; suggesting that boundary layer dynamics (during wintertime) play an important role in efficient trapping of pollutants within the Indo-Gangetic Plain (northern India). The WSOC/OC ratios are fairly uniform (～0.35) in aerosols over urban sites but relatively enhanced contribution of WSOC and higher ratios (～0.5) at a high-altitude site emphasizes the significance of secondary organic aerosols. The comprehensive data set on EC, OC and WSOC/OC ratios from northern India is crucial to improve model parameterization of carbonaceous aerosols for atmospheric scattering and absorption of solar radiation on a regional scale.     

Development of an Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) for Determination of Fine and Ultrafine Metal Aerosols

An Aerosol Focusing-Laser Induced Breakdown Spectroscopy (Aerosol Focusing-LIBS) with a sheath air focusing and an aerodynamic lens focusing was developed to determine elemental composition of fine and ultrafine metal aerosols. Data showed that with a sheath air focusing, the LIBS qualitatively detected various metals (Al, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Zn) in submicrometer to micrometer aerosols, but that detection of ultrafine particles smaller than 100 nm was not successful due to weak intensity of emitted light. Also, the hitting rate was so low for particles at low number concentration and the single particle detection approach was only valid when aerosol loading is low. Thus, we concentrated aerosols on to a collection substrate by using the aerodynamic lens focusing system, resulting in the strong emission light from the generated plasma even for nanoparticles and the better quantification performance by the LIBS. We found the linear relationship between LIBS signal response and metal mass concentration. For example, as Cu metal concentration increased, peak area of LIBS emission line for Cu increased. The resulting correlation coefficient was 0.94 and the LOD for Cu mass concentration was found to be ～80 ng/m3, which can be further lowered by extending current collection time (～5 min). A similar linear relationship was found for Cd and Ni ultrafine metal aerosols. We also successfully detected internally mixed metal aerosols. When particles were collected on a substrate with the aerodynamic lens for 5 min prior to analysis of the deposit it was possible to analyze particles as small as 60 nm.     

Development and Evaluation of a High-Volume Aerosol-into-Liquid Collector for Fine and Ultrafine Particulate Matter

This study presents a novel high-volume aerosol-into-liquid collector, developed to provide concentrated slurries of fine and/or ultrafine particulate matter (PM) to be used for unattended, in situ measurements of PM chemistry and toxicity. This system operates at 200 liters per minute (L/min) flow and utilizes the saturation–condensation, particle-to-droplet growth component of the versatile aerosol concentration enrichment system (VACES), growing fine or ultrafine PM to 3–4-μm droplets, in conjunction with a newly designed impactor, in which grown particles are collected gradually forming highly concentrated slurries. Laboratory evaluation results indicated an excellent overall system collection efficiency (over 90%) for both monodisperse and polydisperse particles in the range of 0.01 to 2 μm. Field evaluations illustrated that overall a very good agreement was obtained for most PM_2.5 species between the new aerosol collection system and the VACES/BioSampler tandem as well as filter samplers operating in parallel. Very good agreement between the new system and the VACES/BioSampler was also observed for reactive oxygen species (ROS) in ambient PM_2.5 samples, whereas lower ROS values were obtained from the water extracts of the filter, likely due to incomplete extraction of water insoluble redox active species collected on the filter substrate. Moreover, the field tests indicated that the new aerosol collection system could achieve continuous and unattended collection of concentrated suspensions for at least 2 to 3 days without any obvious shortcomings in its operation. Both laboratory and field evaluations of the high-volume aerosol-into-liquid collector suggest that this system is an effective technology for collection and characterization of ambient aerosols.

Copyright 2013 American Association for Aerosol Research     

Evaluation of a High Volume Aerosol Concentrator

A virtual impactor sampler, which is designed to concentrate aerosols from a 1000 L/min ambient air sample into a 1 L/min exhaust airflow stream, was tested with near monodisperse aerosols in aerosol wind tunnels to characterize sampling performance. New methodology is introduced to correct results for the presence of doublet and satellite aerosol particles that can be present in the particle size distribution from a vibrating jet atomizer. Aerosol penetration from the free stream near the sampler inlet to the outlet of the device has a peak value of 78% at a particle size of 3.9 w m AD. Sampling effectiveness, which is the mean penetration over the size range of 2.5 to 10 w m AD, is 48%. There are 4 virtual impaction stages in the sampler, and examination of the regional losses shows that most of the aerosol deposition occurs on surfaces of the last 2 stages. The ideal power expenditure of the sampler (excluding electrical and frictional losses in the motor and bearing losses in the blower) is 58 watts as compared to the actual power consumption of 320 watts.