Showing papers in "Aerosol Science and Technology in 2001"
TL;DR: The authors revisited common assumptions for estimating PM2.5 mass concentration and found that these assumptions can be used to estimate organic mass in a wide range of scenarios, such as PM1.5.
Abstract: (2001). Species Contributions to PM2.5 Mass Concentrations: Revisiting Common Assumptions for Estimating Organic Mass. Aerosol Science and Technology: Vol. 35, No. 1, pp. 602-610.
1,842 citations
TL;DR: In this article, the authors present a review of scattering and absorption of light by fractal aggregates, which are typically diffusion limited cluster aggregates with fractal dimensions of D.
Abstract: This paper presents a review of scattering and absorption of light by fractal aggregates. The aggregates are typically diffusion limited cluster aggregates (DLCA) with fractal dimensions of D
1,027 citations
TL;DR: In this paper, the IMPROVE and NIOSH thermal evolution protocols were applied to 60 ambient and source samples from different environments using the same instrument to quantify differences in implemented protocols.
Abstract: Organic carbon (OC) and elemental carbon (EC) are operationally defined by the analysis methods, and different methods give in different results. The IMPROVE (Interagency Monitoring of Protected Visual Environments) and NIOSH (National Institute of Occupational Safety and Health) thermal evolution protocols present different operational definitions. These protocols are applied to 60 ambient and source samples from different environments using the same instrument to quantify differences in implemented protocols on the same instrument. The protocols are equivalent for total carbon sampled on quartz-fiber filters. NIOSH EC was typically less than half of IMPROVE EC. The primary difference is the allocation of carbon evolving at the NIOSH 850°C temperature in a helium atmosphere to the OC rather than EC fraction. Increasing light transmission and reflectance during this temperature step indicate that this fraction should be classified as EC. When this portion of NIOSH OC is added to NIOSH EC, the IMPROVE and ...
857 citations
TL;DR: In this article, a modified ver- sion of a particle size magnifier (Okuyama et al. 1984) is employed to activate and grow particles comprising the fine aerosol mass.
Abstract: We report on a new instrument developed for rapid automated on-line and continuous measurement of ambient aerosol bulk com- position.The general approach is based on earlier devices (Khlystov et al. 1995; Simon and Dasgupta 1995) in which ambient particles are mixed with saturated water vapor to produce droplets easily collected by inertial techniques. The resulting liquid stream is analyzed with an ion chromatograph to quantitatively measure the bulk aerosol ionic components. In this instrument, a modified ver- sion of a particle size magnifier (Okuyama et al. 1984) is employed to activate and grow particles comprising the fine aerosol mass. A single jet inertial impactor is used to collect the droplets onto a vertical glass plate that is continually washed with a constant water diluent flow of nominally 0.10 ml min-1
424 citations
TL;DR: As part of EPRI's Aerosol Research Inhalation Epidemiology Study (ARIES), measurements of aerosol size distributions in the 3 nm to 2 nm range were taken as mentioned in this paper.
Abstract: As part of EPRI's Aerosol Research Inhalation Epidemiology Study (ARIES), measurements of aerosol size distributions in the 3 nm to 2
333 citations
TL;DR: In this article, a symmetric, dichotomous branching alveolar airway structure was attached to the end of the conducting airway tree of each lung structure and the total volume of the alveoral region was the same among the lung geometries.
Abstract: Predicting the amount of particle deposition in the human lung following exposure to airborne particulate matter is the first step toward evaluating risks associated with exposure to airborne pollutants. Realistic deposition models are needed for accurate predictions of deposition in the lung, but a major limitation is the degree to which the lung geometry can be accurately reconstructed. Morphometric data for the entire airway tree of the human lung are not available. So far, idealistic lung structures have been used for deposition calculations. In this study, 10 statistical lung structures based on morphometric measurements of Raabe et al. (1976) were generated for the conducting airways of the human lung. A symmetric, dichotomous branching alveolar airway structure was attached to the end of the conducting airway tree of each lung structure. The total volume of the alveolar region was the same among the lung geometries. Using a mathematical scheme developed previously (Anjilvel and Asgharian 1995), reg...
309 citations
TL;DR: Particle size distributions were measured indoors and outdoors of a single, detached residence during the Fresno particulate matter exposure studies in winter (February 1-28, 1999) and spring (April 18-May 16, 1999).
Abstract: Particle size distributions were measured indoors and outdoors of a single, detached residence during the Fresno particulate matter exposure studies in winter (February 1-28, 1999) and spring (April 18-May 16, 1999). Data was collected for particle sizes ranging from about 0.01 to 2.5
177 citations
TL;DR: In this paper, the processes of particle removal from infiltrating air by building envelopes are simulated in a chamber consisting of two compartments, each having a volume of 19 m3.
Abstract: Several recent studies have indicated significant health risks associated with exposure to fine particles as measured outdoors. However, much of the exposure is believed to have occurred indoors. Consequently, there is considerable interest in the relationship between indoor and outdoor fine particles. This paper describes some results from a study in which the processes of particle removal from infiltrating air by building envelopes are simulated in a chamber. The chamber consists of two compartments, each having a volume of 19 m3. Particles with aerodynamic diameters in the range of 0.05 to 5
175 citations
TL;DR: Cell water sorption and inactivation response was similar for each of the pure cultures tested: when RH exceeded approximately 50%, sorption increased markedly and a sharp concurrent drop in UV-induced inactivation rate was observed.
Abstract: Ultraviolet germicidal irradiation (UVGI) as an engineering control against infectious bioaerosols necessitates a clear understanding of environmental effects on inactivation rates. The response of aerosolized Serratia marcescens, Bacillus subtilis, and Mycobacterium parafortuitum to ultraviolet irradiation was assessed at different relative humidity (RH)levels in a 0.8 m3 completely-mixed chamber. Bioaerosol response was characterized by physical factors including median cell aerodynamic diameter and cell water sorption capacity and by natural decay and UV-induced inactivation rate as determined by direct microscopic counts and standard plate counts. All organisms tested sorbed water from the atmosphere at RH levels between 20% and 95% (up to 70% of dry cell mass at 95% RH); however, no concomitant change in median aerodynamic diameter in this same RH range was observed. Variations in ultraviolet spherical irradiance were minor and not statistically significant in the 20-95% RH range. Cell water sorption...
159 citations
TL;DR: In this article, a new dosimetry model was proposed to calculate the transport and fate of inhaled particulate matter in the human lungs by solving a variant of the general dynamic equation for the size evolution of respirable particles within the human tracheobronchial airways.
Abstract: Transport and fate of inhaled particulate matter in the human lungs is calculated for realistic physicochemical conditions by a new dosimetry model. The model solves a variant of the general dynamic equation for the size evolution of respirable particles within the human tracheobronchial airways, starting at the tracheal entrance. We focus on ambient anthropogenic aerosols, which are of concern in inhalation toxicology because of their potential irritant and toxic effects on humans. The aerosols considered are polydisperse with respect to size and heterodisperse with respect to thermodynamic state and chemical composition, having initially bimodal lognormal size distribution that evolves with time as a result of condensation-evaporation and deposition processes. The architecture of the human lung is described by Weibel's symmetric bronchial tree. Simulations reveal that, due to the rapid growth of submicron-sized particles, increased number and mass fractions of the particle population can be found in the...
138 citations
TL;DR: In this paper, the authors determined temporal and spatial variation of airborne concentrations of viable fungi in two single-family houses during the period of the year that such levels are mostly determined by indoor sources.
Abstract: The aim of this study was to determine temporal and spatial variation of airborne concentrations of viable fungi in 2 single-family houses during the period of the year that such levels are mostly determined by indoor sources. One of the subject residences had moisture problems (the index residence), the other did not have any moisture problems (the reference residence). The concentrations of viable fungi in indoor air were determined a total of 6 times during the winter with 2 six-stage impactors (Andersen 10-800) in 2 rooms in both of the houses. The total concentrations of viable fungi and concentrations of Penicillium, Aspergillus, and Aspergillus versicolor
TL;DR: The chemical composition of PM2.5 was investigated at four sites (Rubidoux, CA, Phoenix, AZ, Philadelphia, PA, and Research Triangle Park, NC) in January and February of 1999 as mentioned in this paper.
Abstract: The chemical composition of PM2.5 was investigated at four sites (Rubidoux, CA, Phoenix, AZ, Philadelphia, PA, and Research Triangle Park, NC) in January and February of 1999. Three samplers were used to determine both the overall mass and the chemical composition of the aerosol. Teflon filters were weighed for total mass. Ions were analyzed using ion chromatography. Elements were determined using X-ray fluorescence. Organic and elemental carbon were measured using a thermo-optical method. At all of the sites, reconstructed mass was observed to be greater than or equal to the measured mass. Good ionic balance was found for ammonium, nitrate, and sulfate at each of the sites. Overall, the chemical composition of the aerosol for each site was in good agreement with the expected composition based upon previous studies, with the exception of relatively high nitrate contribution to the total mass at Philadelphia. Good agreement was found between the predicted amount of sulfate by XRF analysis of sulfur and the...
TL;DR: In this paper, a time-dependent indoor air quality model incorporating all potential particle sources and loss mechanisms was proposed, and Monte Carlo simulations of the model identified the mechanisms such as particle loss during penetration through the building envelope, that modify the outdoor particle size distribution during transport into the interior of a building, calculated indoor-to-outdoor (I/O) concentration ratios, and estimated penetration factors as a function of particle size.
Abstract: The PM2.5 standard proposed by the U.S. Environmental Protection Agency (EPA) has stimulated research on the relationships between particulate matter concentrations and the exposures and subsequent health responses of sensitive subpopulations, such as the elderly. Since individuals in these subpopulations may spend more than 90% of their time indoors, understanding the relationship between outdoor particle concentrations and those found in indoor microenvironments is critical. This research resulted in a time-dependent indoor air quality model incorporating all potential particle sources and loss mechanisms. Monte Carlo simulations of the model identified the mechanisms, such as particle loss during penetration through the building envelope, that modify the outdoor particle size distribution during transport into the interior of a building, calculated indoor-to-outdoor (I/O) concentration ratios, and estimated penetration factors as a function of particle size. Indoor particle generation and transport of ...
TL;DR: In this article, a method has been developed to estimate average concentrations and size distributions with a miniature passive aerosol sampler, which is intended to monitor ambient, indoor or occupational aerosols and has potential utility as a personal sampler.
Abstract: A method has been developed to estimate average concentrations and size distributions with a miniature passive aerosol sampler. To use the passive sampler, one exposes it to an environment for a period of hours to weeks. The passive sampler is intended to monitor ambient, indoor, or occupational aerosols and has potential utility as a personal sampler. The sampler is inexpensive and easy to operate and is capable of taking long-term samples to investigate chronic exposures. After sampling, the passive sampler is covered and brought to the lab. Scanning electron microscopy (SEM) and automated image analysis are used to count and size collected particles with dp
TL;DR: In this paper, a deposition model that accounts for hygroscopic growth, coagulation, particle charge, and cloud behavior of CSP has been presented, along with the effect of smoking patterns.
Abstract: Understanding tobacco related cancer etiology requires the knowledge of cigarette smoke particle (CSP) deposition. Measurements of CSP deposition are inconsistent with typical deposition data. A deposition model that accounts for hygroscopic growth, coagulation, particle charge, and cloud behavior of CSP has not yet been presented. Nor have smoking patterns been accounted for in either deposition measurements or computer models. The dosimetry of Benzo[a]pyrene (BaP), which would add critical information to the relationship between anatomic site preferences of tumors and their histology, is currently unknown. The deposition model presented in this study is the first to accurately account for the dynamic behavior of CSP. Using the model results, the effects of each dynamic behavior on deposition is examined along with the effect of smoking patterns. The dosimetry of BaP is also calculated. The results indicate that coagulation, hygroscopicity, and particle charge increase the total deposition by 16% over th...
TL;DR: In this article, a model for the characteristic time for silica sintering is proposed defining a minimum primary particle diameter above which macroscopic expressions are applied, which is selected consistently with molecular dynamics simulations.
Abstract: The formation and growth of gas-made silica particles by co-agulation and sintering is investigated theoretically. A model for the characteristic time for silica sintering is proposed defining a minimum primary particle diameter above which macroscopic expressions are applied. The value of the minimum primary particle diameter is selected consistently with molecular dynamics simulations. The proposed characteristic sintering time is tested using a monodisperse model for aggregate dynamics by coagulation and sintering. The model predictions are compared with experimental data for silica formation and growth in premixed flames and hot wall aerosol flow reactors by oxidation of hexamethyl-disiloxane (HMDSO) and silicon-tetrachloride (SiCl4).
TL;DR: In this article, a new method of collecting size-fractionated atmospheric aerosol samples for the purpose of directly measuring their transmission and reflectance spectra followed by the determination of the complex refractive index across the entire atmospherically relevant spectral range.
Abstract: To adequately assess the effects of atmospheric aerosols on climate, their optical constants (scattering and absorption coefficients) must be known. The absorption and scattering coefficients of the aerosols are derived from the real and imaginary parts of the complex refractive index and are dependent on their size and chemical composition. Because aerosol properties vary significantly with location, it is difficult to assign values for the absorption and scattering of solar radiation by aerosols in models of global climate change. This study reports a new method of collecting size-fractionated atmospheric aerosol samples for the purpose of directly measuring their transmission and reflectance spectra followed by the determination of the complex refractive index across the entire atmospherically relevant spectral range. The samples were collected with a modified Sierra high-volume cascade impactor with the usual filter collection surfaces replaced with Teflon sheets machined to hold quartz (ultraviolet [...
TL;DR: In this article, the authors measured the hygroscopic behavior of Pasadena, CA aerosol from August 15 to September 15, 1999 using a tandem differential mobility analyzer, and two dry particle sizes were sampled, 50 nm and 150 nm in diameter; humidity of the dry aerosol was carried out at 89% relative humidity.
Abstract: The hygroscopic behavior of Pasadena, CA aerosol was continuously measured from August 15 to September 15, 1999 using a tandem differential mobility analyzer. Two dry particle sizes were sampled, 50 nm and 150 nm in diameter; humidification of the dry aerosol was carried out at 89% relative humidity. Complex growth patterns were observed for both size modes, with aerosol distributions splitting from a single mode at times to more than 6 modes. Diurnal profiles for the observed multiple peaks were noted, with the greatest number of measurable growth modes being found during the late night and predawn hours for 50 nm particles. For 150 nm particles, more modes were present during the afternoon hours, with the humidified aerosol becoming bimodal during the late night/early morning hours. Growth factors, defined as the ratio of humidified particle diameter (at 89%) to dry diameter, were determined for modes with significant number concentrations. Average growth factors over the sampling period for the 2 parti...
TL;DR: In this article, a personal multipollutant sampler was developed for measuring exposures to particulate matter and criteria gases, which can be used for measuring exposure to carbon dioxide and nitrogen dioxide.
Abstract: A personal multipollutant sampler has been developed. This sampler can be used for measuring exposures to particulate matter and criteria gases. The system uses asingle personalsampling pump that operates at a flow rate of 5.2 l/min. The basic unit consists of two impaction-based samplers for PM2.5 and PM10 attached to a single elutriator. Two mini PM2.5 samplers are also attached to the elutriator for organic carbon (OC), elemental carbon (EC), sulfate, and nitrate measurements. For the collection of nitrate and sulfate, the minisampler includes a miniaturized honeycomb glass denuder that is placed upstream of the filter to remove nitric acid and sulfur dioxide and to minimize artifacts. Two passive samplers can also be attached to the elutriator for measurements of gaseous copollutants such as O3, SO2, and NO2. The performance of the multipollutant sampler was examined through a series of laboratory chamber tests. The results showed a good agreement between the multipollutant sampler and the reference m...
TL;DR: In this article, the influence of denuder sampling methods and filter collection media on the measurement of semi-volatile organic carbon (SVOC) associated with PM2.5 was evaluated.
Abstract: This study evaluates the influence of denuder sampling methods and filter collection media on the measurement of semi-volatile organic carbon (SVOC) associated with PM2.5. Two types of collection media, charcoal (activated carbon) and XAD, were used both in diffusion denuders and impregnated back-up filters in two different samplers, the VAPS and the PC-BOSS. The two organic diffusion denuders were XAD-coated glass annular denuders and charcoal-impregnated cellulose fiber filter (CIF) denuders. In addition, recently developed XAD-impregnated quartz filters were compared to CIF filters as back-up filter collection media. The two denuder types resulted in equivalent measurement of particulate organic carbon and particle mass. The major difference observed between the XAD and charcoal BOSS denuders is the higher efficiency of charcoal for collection of more volatile carbon. This more volatile carbon does not contribute substantially to the particle mass or SVOC measured as OC on quartz filters downstream of ...
TL;DR: In the national ambient air quality standards specified by the U.S. Environmental Protection Agency in the Code of Federal Regulations, new standards were established for particulate matter on July 18, 1997 as discussed by the authors.
Abstract: In the national ambient air quality standards specified by the U.S. Environmental Protection Agency in the Code of Federal Regulations, new standards were established for particulate matter on July 18, 1997. The new particulate matter standards specify mass concentration as the indicator for fine particulate matter (aerodynamic diameter of 2.5
TL;DR: In this article, computer-controlled scanning electron microscopy (CCSEM) coupled with energy-dispersive X-ray analysis (EDX) allows automated analysis of particle size, chemistry, and particle classification.
Abstract: Concerns about the environmental and public health effects of particulate matter (PM) have stimulated interest in analytical techniques capable of measuring the size and chemical composition of individual aerosol particles. Computer-controlled scanning electron microscopy (CCSEM) coupled with energy-dispersive X-ray analysis (EDX) allows automated analysis of particle size, chemistry, and particle classification. In combination with manual SEM and bulk analytical techniques such as X-ray fluorescence, CCSEM can be a valuable tool for characterizing individual ambient particles and determining sources of ambient PM. The goal of this study was to examine several issues related to the quality and validity of CCSEM data. These included the stability of unattended CCSEM for multihour runs, the number of particles that must be analyzed in order to yield representative results, and errors associated with CCSEM. CCSEM was applied to the analysis of a 24 h ambient particle sample collected in Baltimore, MD. The co...
TL;DR: The well impactor ninety-six (WINS) was designed and calibrated to serve as a particle size separation device for the EPA reference method sampler for particulate matter under 2.5 as discussed by the authors.
Abstract: The EPA well impactor ninety-six (WINS) was designed and calibrated to serve as a particle size separation device for the EPA reference method sampler for particulate matter under 2.5
TL;DR: In this article, the mass fraction of solute (mfs), defined as the ratio of the dry solute mass to the solution mass, of the additives was measured as a function of relative humidity (RH) at equilibrium.
Abstract: balance (EDB). The mass fraction of solute (mfs), dee ned as the ratio of the dry solute mass to the solution mass, of the additives was measured as a function of relative humidity (RH) at equilibrium. Bulk measurements and literature data suggest that these three additives all crystallize at their respective saturation conditions. However, crystallization or deliquescence was not observed for the suspended particles of the three additives. They behave as nondeliquescentmaterialsandsorbanddesorbwaterreversibly.At RH = 5%,citricacidparticlesstillcontain » 8wt%residualwater, which corresponds to a stoichiometry of citric acid monohydrate. Glucose and sorbitol particles are essentially water-free. Universal FunctionalActivityCoefe cient (UNIFAC)modelpredictsthewater activities of glucose, citric acid, and sorbitol (expressed as mfs of the particles ) to within §16%, 24%, and 6% of those determined by the EDB, respectively.
TL;DR: In this article, the authors determined the deposition pattern of nanometer-sized particles in the human tracheobronchial (TB) airways of children and young adults.
Abstract: Inhalation exposure to ultrafine particles, including radon progeny and other combustion aerosols, has been implicated in potential health risks of ambient and indoor environments. These particles deposit in the respiratory tract mainly by diffusion. The purpose of this study was to determine the deposition pattern of nanometer-sized particles in the human tracheobronchial (TB) airways of children and young adults. The deposition was determined for 1.75, 10, and 40 nm 212Pb particles at flow rates corresponding to respiratory minute volumes at rest and during moderate exercise. The 1.75 nm particles were unattached clusters, whereas the 10 and 40 nm particles were silver particles with attached 212Pb clusters. Replicate casts of the upper TB airways of 3, 16, and 23 year old humans were used, including the larynx, trachea, and bronchial airways down to generations 5-8. Deposition in each generation and total deposition were measured by counting the 212Pb gamma photopeak in a NaI (Tl) detector. The effects...
TL;DR: In this paper, the authors describe an integrated measurement method that can continuously monitor the total surface area, as well as the total number and volume, of atmospheric aerosols, using three integral aerosol sensors: a condensation particle counter (CPC), a mass concentration monitor (MCM), and an electrical aerosol detector (EAD).
Abstract: While surface area is one of the most important atmospheric aerosol properties in health effects, methods for online measurement of surface area are not widely available and/or require complex operations. In this paper, we describe an integrated measurement method that can continuously monitor the total surface area, as well as the total number and volume, of atmospheric aerosols. Three integral aerosol sensors - (i) a condensation particle counter (CPC) for number concentration measurement, (ii) a mass concentration monitor (MCM) for mass concentration measurement, and (iii) an electrical aerosol detector (EAD) for current measurement of charged aerosol - are used in this study. Signals from the three sensors are converted into a lognormal size distribution by minimizing the difference between the measured signals and the theoretical values based upon a size distribution model, the instrument calibration, and its theoretical responses. Results from a 20 day continuous sampling period show that the calcul...
TL;DR: In this article, titania particles were produced experimentally by the thermal decomposition of titanium tetraisopropoxide (TTIP) and oxidation of titanium tetrachloride (TiCl 4 ) using a laminar flow aerosol reactor.
Abstract: In the manufacturing of nanometer-sized material particlulates by aerosol gas-to-particle conversion processes, it is important to analyze how the gas-phase chemical reaction, nucleation, agglomeration, and sintering rates control the size distribution and morphology of particles. In this study, titania particles were produced experimentally by the thermal decomposition of titanium tetraisopropoxide (TTIP) and oxidation of titanium tetrachloride (TiCl 4 ) using a laminar flow aerosol reactor. The effect of reaction temperature on the size and morphology of the generated particles was investigated under various conditions. The size distributions of agglomerates were measured using a DMA/CNC system. The size distributions of primary particles were measured using TEM pictures of the agglomerates sampled by a thermophoretic aerosol sampler. In order to model the growth of both agglomerates and primary particles simultaneously, a two-dimensional discrete-sectional representation of the size distribution was em...
TL;DR: Aerosol growth technology is used as a means of collecting ambient aerosol particles for subsequent chemical analyses in this paper, where air is sampled at a flow rate of 170 L.min-1.
Abstract: Aerosol growth technology is used as a means of collecting ambient aerosol particles for subsequent chemical analyses. Condensational growth has previously been used in Condensation Nucleus Counters and in ultrafine particle concentrators at flow rates up to 110 L . min-1. Here, air is sampled at a flow rate of 170 L .min-1
TL;DR: The Real-Time Ambient Mass Sampler (RAMS) as mentioned in this paper is a real-time ambient monitor for the determination of fine particulate mass, including ammonium nitrate and semi-volatile organic material.
Abstract: The Real-Time Ambient Mass Sampler (RAMS) is a real-time ambient monitor for the determination of fine particulate mass, including ammonium nitrate and semi-volatile organic material. Fine particulate mass is continuously measured with a TEOM monitor containing a "sandwich" filter to trap any semi-volatile material (nitrate and organic) lost from collected particles. Gas phase compounds which will interfere with the TEOM monitor measurement are removed using a particle concentrator,diffusion denuders, and dryers. The concentrations of these gas phase species are reduced to manageable, but not zero, concentrations prior to the collection of particles on the TEOM probe. Therefore a second, parallel system preceded by a filter is used to obtain an active blank for the correction of the RAMS monitor data. The results obtained for the continuous determination of PM2.5 with the RAMS have been validated by comparison with results obtained from PC-BOSS diffusion denuder integrated samples to determine the mass of...
TL;DR: In this article, an eight-stage impactor was connected to the tunnel with an isoaxial, isokinetic probe and was equipped with polycarbonate-membrane substrates saturated with oleic acid to minimize particle bounce.
Abstract: Wind tunnel experiments have been performed on a passive aerosol sampler. The sampler estimates average concentrations and size distributions using a deposition velocity model and the measured particle flux to the sampler. The small-scale wind tunnel incorporated a high-output aerosol generator that produced nonvolatile, polydisperse particles. An eight-stage impactor was connected to the tunnel with an isoaxial, isokinetic probe and was equipped with polycarbonate-membrane substrates saturated with oleic acid to minimize particle bounce. Before performing experiments, the tunnel's test section was characterized. Aerosol concentrations were determined to have a CV < 6%. The friction velocity, an index of turbulence, was found to range from 0.09 to 0.25 m/s for wind speeds of 1.5 to 5 m/s. The empirical portion of the deposition velocity model, γm, was determined as a function of particle size by minimizing the sum-of-squares difference between impactor and passive sampler across all size bins and all experiments. The relatively simple correlation is a function of the particle Reynolds number only. Precision was assessed by running three passive samplers simultaneously in each experiment. The tests yielded CV PM2.5 = 18.1% and CV PM10 = 32.2%. ANOVA tests were conducted on accuracy and precision to see whether they depended on wind speed, relative humidity, or aerosol concentration, and accuracy was tested with respect to particle size. No significant trends were observed. Sensitivity analysis showed that the volume shape factor is the most important of the mass and shape conversion factors. If SEM is used, the passive sampler will exhibit some error when sampling volatile aerosols. Because concentrations fluctuate over time, long-term exposures measured by the passive sampler should be more accurate than conventional averages based on short-term samples.