Reliable assessment of personal exposure to air pollution remains a challenge due to the limitations of monitoring technology. Recent technology developments, such as reductions in the size and cost of samplers as well as incorporation of continuous sensors for location, activity, and exposure (i.e., global positioning systems [GPS], accelerometers, and low-cost pollutant sensors), have advanced our ability to assess personal exposure to air pollution. This study evaluated the upgraded Ultrasonic Personal Aerosol Sampler (UPAS v2.1 PLUS) as a tool for quantifying time-integrated indoor and personal exposure to particulate matter (PM) and black carbon (BC) among a panel of participants in California's Central Valley and exploring personal exposures in different microenvironments using time/location-resolved PM data. Three field campaigns demonstrated that filter-derived PM, PM, PM BC, and PM BC concentrations measured using the UPAS were linear, unbiased, and precise compared to those measured using conventional personal sampling equipment. Time-resolved PM, GPS, and light intensity data from the UPAS allowed for personal PM exposure assessment across microenvironments. The majority of daily PM exposure occurred inside the home. Participants with higher out-of-home PM exposures received those exposures primarily in agricultural and in-transit environments, in accordance with their self-reported occupational exposures. This study demonstrated the UPAS v2.1 PLUS is a reliable and valid tool for characterizing indoor air pollution and personal exposures in both temporal and spatial dimensions. Its enhanced capabilities should reduce the burden of personal activity logging in the field and enable accurate and precise estimation of exposures for epidemiological and community-based research.

Elevated concentrations of fine particulate matter (PM, particles < 2.5 m) lead to negative health outcomes in urban areas, such as New York City (NYC). The sources of particles contributing to PM in NYC are variable and complex due to the range of primary anthropogenic and biogenic emissions, as well as secondary aerosol formation (i.e., aging) from gaseous precursors. To improve understanding of the contributors to PM, single particle microspectroscopy uses chemical fingerprints to identify sources and the extent of aging, but few studies have integrated multiple microspectroscopy methods to understand PM in NYC. Herein, we focus on a recently-developed form of microspectroscopy that can measure atmospherically-sized particles (>~0.8 m), optical photothermal infrared (O-PTIR). We compare O-PTIR to existing microspectroscopy methods [Raman, fluorescence, and energy dispersive X-ray (EDX)] to study sources and aging of the complex NYC aerosol based on functional group and elemental information, which we also relate to bulk mass spectrometry methods. Single particle data shows submicron aerosol composition dominated by carbonaceous particles that fluoresce mixed with ammonium and sulfate, with a range of oxidized organic functional groups observed. At larger sizes, more primary sources (salts, dust, and biological) were observed, with nitrate being the dominant secondary anion. Collectively, the results from OPTIR and other instruments across case-study days reveal variations in sources and aging, with greater variability at larger diameters. Demonstrating the potential of O-PTIR when combined with the other methods to provide data that is important for improving air quality in urban megacities.

A "Community Condensation Particle Counter" (cCPC) has been developed to provide an affordable monitor of airborne particle number concentrations. The cCPC is an expansion-type condensation particle counter that incorporates single particle counting to yield a direct measurement of number concentration. Particle number concentrations are derived from the detection of individual droplets exiting the cell during the expansion, combined with the pressure readings and the physical volume of the particle cell. Modeling and experiment confirm detection of particles as small as 4 nm, with >95% detection above 20 nm. For 12 days of ambient sampling two collocated cCPCs exhibit a pooled standard deviation of 3.5%. Comparison to a pair of benchtop instruments (ADI MAGIC CPCs) yields a correlation of R=0.98 and a regression slope of 1.1. Laboratory studies at concentrations higher than 3×10 cm for both sulfate and dioctyl sebacate show equally reduced response when compared to a versatile water CPC, but this was not observed in ambient aerosol sampling. Further research will be needed to resolve this discrepancy.

Exposure to airborne respiratory viruses can be a health hazard in occupational settings. In this study, air sampling was conducted from January to March 2023 in two outpatient medical clinics-one primary care clinic and one clinic dedicated to the diagnosis and treatment of respiratory illnesses-for the purpose of assessing airborne respiratory virus presence. Work involved the operation of a BioSpot-VIVAS as a stationary air sampler and deployment of NIOSH BC-251 bioaerosol samplers as either stationary devices or personal air samplers worn by staff members. Results were correlated with deidentified clinical data from patient testing. Samples from seven days were analyzed for SARS-CoV-2, influenza A H1N1 and H3N2 viruses, and influenza B Victoria- and Yamagata-lineage viruses, with an overall 17.5% (17/97) positivity rate. Airborne viruses predominated in particles of aerodynamic diameters from 1-4 μm and were recovered in similar quantities from both clinics. BC-251 samplers (17.4%, 15/86) and VIVAS (18.2%, 2/11) collected detectable viruses at similar rates, but more numerous BC-251 samplers provided greater insight into virus presence across clinical spaces and job categories. 60% of samples from reception areas contained detectable virus, and exposure to significantly more virus (p = 0.0028) occurred at reception desks as compared to the "mobile" job categories of medical providers and nurses. Overall, this study provides valuable insights into the impacts of hazard mitigation controls tailored to reducing respiratory virus exposure and highlights the need for continued diligence toward exposure risk mitigation in outpatient medical clinics.

Airborne transmission plays a significant role in the transmission of respiratory diseases such as COVID-19, for which the respiratory aerosol droplets are responsible for the transportation of potentially infectious pathogens. However, the aerosol physicochemical dynamics during the exhalation process are not well understood. The representativeness of respiratory droplet surrogates of exhaled aerosol and suspension media for aerosols currently used for laboratory studies remains debated. Here, we compare the evaporation kinetics and equilibrium thermodynamics of surrogate respiratory aerosol droplets including sodium chloride, artificial saliva (AS) and Dulbecco's modified Eagle's medium (DMEM) by using the Comparative Kinetics Electrodynamic Balance. The potential influences of droplet composition on aerosol hygroscopic response and phase behavior, and the influence of mucin are reported. The equilibrium hygroscopicity measurement was used to verify and benchmark the prediction of evaporation kinetics of complex solutions using the Single Aerosol Particle Drying Kinetics and Trajectory model. We show that the compositionally complex culture media which differs from sodium chloride and artificial saliva (mucin-free solutions). The DMEM evaporation dynamics contained three distinctive phases when drying at a range of humidities, including a semi-dissolved phase when evaporating at the environmental humidity range. The effect of mucin on droplet evaporation and phase behavior at low RH were compared between AS and DMEM solutions. In both cases, mucin delayed the crystallization time of the droplets, but it promoted phase change (from homogenous to semi-dissolved/spherical with inclusions) to occur at higher water activities.

Diesel particulate matter (DPM) is a common and well-known health hazard in the mining environment. The regulatory method for monitoring both the organic and elemental carbon (OC, EC) portions of DPM is a laboratory-based thermal-optical method with a typical turnaround time of one week. In order to evaluate exposure levels and take corrective action prior to overexposure, a portable real-time device capable of quantifying both OC and EC is needed. To that end, researchers from the National Institute for Occupational Safety and Health (NIOSH) designed and tested the feasibility of a device based on bandpass optical filters that target key infrared wavelengths associated with DPM and its spectroscopic baseline. The resulting device, referred to here as a non-dispersive infrared (NDIR) spectrometer could serve as the basis of a cost-effective, field-portable alternative to the laboratory thermal-optical method. The limits of quantification (LOD) indicate that the NDIR spectrometer can quantify EC, OC, and TC provided they are present at 20, 37, and 46 μg/m or more, respectively. In the event that the NDIR spectrometer is integrated with a sampler and filter tape the LOD is estimated to be reduced to 13, 7, and 10 μg/m for EC, OC, and TC, respectively. These LOD estimates assume a face velocity of 59 cm/s and a sampling time of 30 min.

The COVID-19 pandemic has raised interest in using chemical air treatments as part of a strategy to reduce the risk of disease transmission, but more information is needed to characterize their efficacy at scales translatable to applied settings and to develop standardized test methods for characterizing the performance of these products. Grignard Pure, a triethylene glycol (TEG) active ingredient air treatment, was evaluated using two different test protocols in a large bioaerosol test chamber and observed to inactivate bacteriophage MS2 in air (up to 99.9% at 90 min) and on surfaces (up to 99% at 90 min) at a concentration of approximately 1.2 - 1.5 mg/m. Introducing bioaerosol into a TEG-charged chamber led to overall greater reductions compared to when TEG was introduced into a bioaerosol-charged chamber, although the differences in efficacy against airborne MS2 were only significant in the first 15 min. Time-matched control conditions (no TEG present) and replicate tests for each condition were essential for characterizing treatment efficacy. These findings suggest that chemical air treatments could be effective in reducing the air and surface concentrations of infectious pathogens in occupied spaces, although standard methods are needed for evaluating their efficacy and comparing results across studies. The potential health impacts of chronic exposure to chemicals should also be considered, but those were not evaluated here.

E-cigarette aerosols contain a complex mixture of harmful and potentially harmful chemicals. Once released into the environment, they evolve and become new sources of indoor air pollutants that could pose a significant threat to both users and non-users. However, current understanding of the physicochemical properties of e-cigarette aerosol constituents that govern gas-particle partitioning in the atmosphere is limited, making it difficult to estimate the health risks associated with exposure. Here, we used correlation gas chromatography (C-GC) and two-dimensional volatility basis set (2D-VBS) methods to determine the vapor pressures and volatility for commonly reported toxic and irritating e-cigarette aerosol constituents. The vapor pressures of target compounds at 298 K were estimated from the Antoine-type linear relationship between the vapor pressure of reference standards and their retention times. Our C-GC results showed an overall positive correlation (R = 0.84) with estimates using the EPI (Estimation Programs Interface) Suite. The volatility calculated by 2D-VBS correlates well with the calculated vapor pressure from both C-GC (R = 0.82) and EPI Suite (R = 0.85). The volatility distribution also indicated fresh e-cigarette aerosol constituents are mainly more volatile organic compounds. Our case study revealed that low-vapor-pressure compounds (e.g., σ-dodecalactone, γ-decalactone, and maltol) become enriched in the e-cigarette aerosols within 2 hours following vaping emissions. Overall, these findings demonstrate the applicability of the C-GC and 2D-VBS methods for determining the physiochemical properties of e-cigarette aerosol constituents, which can aid in assessing the dynamic chemical composition of e-cigarette aerosols and exposures to vaping emissions in indoor environments.

Most evaluations of low-cost aerosol sensors have focused on their measurement bias compared to regulatory monitors. Few evaluations have applied fundamental principles of aerosol science to increase our understanding of how such sensors work and could be improved. We examined the Plantower PMS5003 sensor's internal geometry, laser properties, photodiode responses, microprocessor output, flow rates, and response to mono- and poly-disperse aerosols. We developed a physics-based model of particle light scattering within the sensor, which we used to predict counting and sizing efficiency for 0.30 to 10 μm particles. We found that the PMS5003 counts single particle scattering events, acting like an imperfect optical particle counter, rather than a nephelometer. As particle flow is not focused into the core of the laser beam, >99% of particles that flow through the PMS5003 miss the laser, and those that intercept the laser usually miss the focal point and are subsequently undersized, resulting in erroneous size distribution data. Our model predictions of PMS5003 response to varying particle diameters, aerosol compositions, and relative humidity were consistent with laboratory data. Computational fluid dynamics simulations of the PurpleAir monitor housing showed that for wind-speeds less than 3 m s, fine and coarse particles were representatively aspired to the PMS5003 inlet. Our measurements and models explain why the PurpleAir overstates regulatory PM in some locations but not others; why the PurpleAir PM is unresponsive to windblown dust; and why it reports a similar particle size distribution for coarse particles as it does for smoke and ambient background aerosol.

A new high-flow, compact aerosol concentrator, using rapid, turbulent mixing to grow aerosol particles into droplets for dry spot sample collection, has been designed and tested. The "TCAC (Turbulent-mixing, Condensation Aerosol Concentrator)" is composed of a saturator for generating hot vapor, a mixing section where the hot vapor mixes with the cold aerosol flow, a growth tube where condensational droplet growth primarily occurs, and a converging nozzle that focuses the droplets into a beam. The prototype concentrator utilizes an aerosol sample flow rate of 4 L min. The TCAC was optimized by varying the operating conditions, such as relative humidity of the aerosol flow, mixing flow ratio, vapor temperature, and impaction characteristics. The results showed that particles with a diameter ≥ 25 nm can be grown to a droplet diameter > 1400 nm with near 100% efficiency. Complete activation and growth were observed at relative humidity ≥ 25% of the aerosol sample flow. A consistent spot sample with a diameter of (the diameter of a circle containing 90% of the deposited particles) was obtained regardless of the aerosol particle diameter ( ). For fiber counting applications using phase contrast microscopy, the TCAC can reduce the sampling time, or counting uncertainty, by two to three orders of magnitude, compared to the 25-mm-filter collection. The study shows that the proposed mixing-flow scheme enables a compact spot sample collector suitable for handheld or portable applications, while still allowing for high flow rates.

The deposition of inhaled particles is typically highly localized in both the bronchial and alveolar region of the lung displaying spot-like, line-like and other deposition patterns. However, knowledge is very limited on how different deposition patterns may influence downstream cellular responses. In this study, the Dosimetric Aerosol Inhalation Device (DAVID) was used for dose-controlled deposition of cupric oxide nanoparticles (CuONPs) in four different patterns (i.e., spot, ring, line and circle) on human alveolar A549 cells cultured at an air-liquid interface (ALI). After CuONP deposition (<15 min) and a 24 h incubation phase, cell viability, apoptotic / necrotic cell count, and gene expressions were measured. At the lowest dose of ~5 μg/cm, the line pattern resulted in the lowest viability of cells (57%), followed by the spot pattern (85%) while the ring and circle patterns exhibited >90% viability, compared to the particle free air control. At the highest dose of ~20 μg/cm, the viability reduced to 44%-60% for all patterns. Also, the gene profile was found to depend on deposition pattern. The results demonstrate that the deposition pattern is a critical parameter influencing cellular response, thus an important parameter to consider in toxicity and drug delivery studies. Furthermore, the ability of DAVID to control the delivery of aerosolized particles in various deposition patterns was demonstrated, which enables implementation of nonhomogeneous particle deposition patterns that mimic real-life human inhalation exposures in future toxicology studies.

Information on microorganisms in indoor air of various institutional and commercial buildings has significant value in a public health management perspective. However, there is a lack of prior research comparing indoor airborne microbiota across different categories of those buildings. We characterized indoor airborne bacteria in 10 buildings (two for each of five categories: train station, parking garage, mart, public library, and daycare center) during summer and winter. The 16S rRNA gene in the bacterial gDNA extracted from samples was quantified using quantitative real-time polymerase chain reaction and sequenced with the Illumina MiSeq platform for characterizing community composition. We collected information on temperature, relative humidity, CO concentration, and particulate matter (PM) concentrations by particle size (<1μm, 1-2.5μm, 2.5-10μm) indoors. We performed a multivariate regression analysis to identify factors influencing bacterial quantity and Permutational Multivariate Analysis of Variance (PERMANOVA) to determine factors affecting cluster dissimilarity. We found that bacterial concentration was significantly (-values < 0.05) associated with season and CO concentration. The PERMANOVA analyses showed the significant (-values < 0.05) associations of bacterial cluster dissimilarity with season, building category, and CO. Our study indicated that the season, and CO concentrations may be important factors associated with the indoor airborne bacterial concentration and composition. Building category and usage appeared to significantly influence the bacterial community composition but not the concentration. Our study may provide basic data on bacterial community composition and their concentration that are needed for properly managing microbial exposures in occupants or customers of the studied institutional and commercial buildings.

A falling powder can generate a dust cloud from its interaction with the ambient air and from its splash onto a substrate. This article reports the results of a numerical simulation study, which attempts to model this second process. We argue that the dust cloud arises from the aerodynamic resuspension of previously deposited small particles. The agglomerated falling powder is modeled as a falling pellet disk impacting a surface covered with a monolayer of previously deposited particles. The Reynolds number of the air flow in the vicinity of the impacting pellet is Re ~ 1860, so the air flow is modeled as laminar and incompressible. The dust particles are incorporated a Lagrangian multiphase treatment. The sudden deceleration of the disk sheds an aerodynamic vortex, which suspends particles from the monolayer. Characteristics of the dust cloud (average and maximum height and radius) are tracked; these are conveniently summarized by following the trajectory of the dust cloud centroid. The probability of aerosolization decreases with distance from the impacted pellet. The centroid trajectory is studied as a function of dust particle size. The model is relatively insensitive to disk radius and thickness. More realistic modeling of dust clouds generated by the splash of falling powders will require a statistical analysis of aggregate size and location, as well as the inclusion of interparticle and particle-surface interactions.

The impact of suspended particles on health, climate, and industrial applications is highly size-dependent. Thus, regulations are typically based on particles with diameters below a specific size, such as particulate matter less than 2.5 μm (PM). For over a century, cyclones have been employed to isolate particles below a certain diameter by removing large particles from a gas stream, but cyclones are typically relatively large, heavy, and expensive to fabricate compared to objects made with low-cost 3-dimensional (3D) printers. Herein, we present one-piece 3D-printed micro-cyclones (PM and PM) to isolate particles smaller than a specific diameter. The collection efficiencies and 50% cut-off diameters (d) of multiple cyclones were evaluated with both monodisperse and polydisperse standards ranging from 0.1 to 3 μm, as well as ambient aerosol. By altering the inlet orientation relative to the micro-cyclone centerline (orthogonal, 50% offset, and fully offset), we show that shifting the inlet radially outward increased the steepness of the transmission curve resulting in a sharper cut-point. The d also decreased below the designed for diameter, (PM = 1.4, 1.0, and 0.9 μm; PM = 3.2, 2.0, 1.9 μm), which was attributed to imperfect models, internal surface roughness, and print errors versus machining. These single piece, 3D-printed cyclones provide a cheaper (< $1), faster, and more accessible approach to manufacture micro-cyclones for use in a range of aerosol applications.

As SARS-CoV-2 swept across the globe, increased ventilation and implementation of air cleaning were emphasized by the US CDC and WHO as important strategies to reduce the risk of inhalation exposure to the virus. To assess whether higher ventilation and air cleaning rates lead to lower exposure risk to SARS-CoV-2, 1274 manuscripts published between April 2020 and September 2022 were screened using key words "airborne SARS-CoV-2 or "SARS-CoV-2 aerosol". Ninety-three studies involved air sampling at locations with known sources (hospitals and residences) were selected and associated data were compiled. Two metrics were used to assess exposure risk: SARS-CoV-2 concentration and SARS-CoV-2 detection rate in air samples. Locations were categorized by type (hospital or residence) and proximity to the sampling location housing the isolated/quarantined patient (primary or secondary). The results showed that hospital wards had lower airborne virus concentrations than residential isolation rooms. A negative correlation was found between airborne virus concentrations in primary-occupancy areas and air changes per hour (ACH). In hospital settings, sample positivity rates were significantly reduced in secondary-occupancy areas compared to primary-occupancy areas, but they were similar across sampling locations in residential settings. ACH and sample positivity rates were negatively correlated, though the effect was diminished when ACH values exceeded 8. While limitations associated with diverse sampling protocols exist, data considered by this meta-analysis support the notion that higher ACH may reduce exposure risks to the virus in ambient air.

The ability to collect size-fractionated airborne particles that contain viable bacteria and fungi directly into liquid medium while also maintaining their viability is critical for assessing exposure risks. In this study, we present the BioCascade impactor, a novel device designed to collect airborne particles into liquid based on their aerodynamic diameter in three sequential stages (>9.74 μm, 3.94-9.74 μm, and 1.38-3.94 μm when operated at 8.5 L/min). Aerosol samples containing microorganisms - either or , were used to evaluate the performance of the BioCascade (BC) paired with either the VIable Virus Aerosol Sampler (VIVAS) or a gelatin filter (GF) as stage 4 to collect particles <1.38 μm. Stages 2 and 3 collected the largest fractions of viable when paired with VIVAS (0.468) and GF (0.519), respectively. Stage 3 collected the largest fraction of viable particles in both BC+VIVAS (0.791) and BC+GF (0.950) configurations. The distribution function of viable microorganisms was consistent with the size distributions measured by the Aerodynamic Particle Sizer. Testing with both bioaerosol species confirmed no internal loss and no re-aerosolization occurred within the BC. Irrespective of the bioaerosol tested, stages 1, 3 and 4 maintained ≥80% of viability, while stage 2 maintained only 37% and 73% of viable and , respectively. The low viability that occurred in stage 2 warrants further investigation. Our work shows that the BC can efficiently size-classify and collect bioaerosols without re-aerosolization and effectively maintain the viability of collected microorganisms.

Biomass burning (BB) is a major source of atmospheric fine carbonaceous aerosols, which play a significant, yet uncertain, role in modulating the Earth's radiation balance. However, accurately representing their optical properties in climate models remains challenging due to factors such as particle size, mixing state, combustion type, chemical composition, aging processes, and relative humidity (RH). In our study, we investigated BB organic-rich aerosols generated from smoldering sub-Saharan African biomass fuels. Fuel samples were collected in Africa and aerosols generated in the laboratory. We quantified key optical parameters, including mass cross-sections for extinction (2.04 ± 0.32 - 15.5 ± 2.48 m/g), absorption (0.04 ± 0.01-0.3 ± 0.1 m/g), and scattering (1.9 ± 0.68-15.3 ± 5.5 m/g). Wavelength-dependent properties were used to determine absorption and scattering Ångström exponents. The single scattering albedo of these aerosols ranged from 0.8 ± 0.03 to 1.0 ± 0.04 and we observed a wavelength-dependent behavior. Extinction emission factors were determined at a wavelength of 550 nm, with values ranging from 42 ± 5 to 293 ± 32 m/kg. Notably, optical properties exhibited fuel-type dependence, with differences observed between hardwood samples and other fuels, such as grass and animal dung. Aging increased mass extinction and scattering cross-sections at 550 nm, while humidity had the opposite effect across all fuels. Nitrate radical oxidation, both in photo and dark aging conditions, also influenced these properties. The findings are expected to close the gap in our understanding of optical properties of BB aerosol emissions in one of the least studied regions of the world - Africa - providing information to climate and air quality models for the region.

Numerous studies rely on long-term PM speciation data from the EPA's Chemical Speciation Network (CSN), for example, to estimate health impacts or investigate the sources and transport of PM pollution. These studies rely on consistent, long-term time series measurements of PM species to draw conclusions about PM emissions sources and their health impacts. However, changes in contractors and associated methodological changes in 2015 and 2018 led to disruptions in the consistency of the CSN data, specifically, concentration discontinuities in the CSN time series for ions and elemental carbon (EC) from November 2015 to September 2018 and from October 2018 onward, respectively. To address the impact of these changes on downstream air quality and health analyses, this study developed correction factors by comparing collocated CSN measurements to measurements from the Interagency Monitoring of Protected Visual Environment (IMPROVE) network, which used consistent instrumentation and contractors throughout the study period. These correction factors reduced the discontinuities in the ions and EC concentration time series data, which could be critical for time series source apportionment receptor modeling, air pollution policy and accountability investigations, and health effect studies.

This study investigates the effectiveness of electrospun nanofibrous filters in capturing polydisperse virus-containing aerosols and the subsequent release of viruses, in comparison with standard commercial filters used in respirators, military gas masks, and devices for airborne virus sampling. We assessed the performance of these filters in capturing and releasing polydisperse aerosols containing MS2 bacteriophage, as well as in their ability to filter monodisperse dioctyl phthalate aerosols measuring 0.185 μm and 0.3 μm in diameter. Our findings indicate that nanofibrous filters provide superior filtration efficiency for monodisperse aerosols, achieving a reduction in the concentration of penetrating aerosols by 2-3 orders of magnitude compared to their commercial counterparts. However, this enhanced efficiency is accompanied by a higher pressure drop and a lower quality factor, underscoring the need for further improvements. Additionally, our research confirms the feasibility of producing aligned nanofibers via multiple-jet needleless electrospinning, though alignment did not significantly impact filtration efficiency. Nanofibrous filters demonstrated filtration efficiency for aerosolized virus-containing particles that was comparable to or better than that of commercial filters. Notably, certain nanofibrous filters exhibited exceptionally low rates of viral aerosol capture and release, indicating a potential for virus neutralization. Moreover, filters made from water-soluble electrospun polyvinylpyrrolidone significantly outperformed those made from gelatin in terms of viral particle release, underscoring the potential of water-soluble electrospun materials in improving viral particle collection. Overall, our study highlights the significant promise of electrospun nanofibers in public health, especially in enhancing defenses against the transmission of viral aerosols.

Airborne transmission of infectious (viable) SARS-CoV-2 is increasingly accepted as the primary manner by which the virus is spread from person to person. Risk of exposure to airborne virus is higher in enclosed and poorly ventilated spaces. We present a study focused on air sampling within residences occupied by individuals with COVID-19. Air samplers (BioSpot-VIVAS, VIVAS, and BC-251) were positioned in primary- and secondary-occupancy regions in seven homes. Swab samples were collected from high-touch surfaces. Isolation of SARS-CoV-2 was attempted for samples with virus detectable by RT-qPCR. Viable virus was quantified by plaque assay, and complete virus genome sequences were obtained for selected samples from each sampling day. SARS-CoV-2 was detected in 24 of 125 samples (19.2%) by RT-qPCR and isolated from 14 (11.2%) in cell cultures. It was detected in 80.9% (17/21) and cultured from 61.9% (13/21) of air samples collected using water condensation samplers, compared to swab samples which had a RT-qPCR detection rate of 10.5% (4/38) and virus isolation rate of 2.63% (1/38). No statistically significant differences existed in the likelihood of virus detection by RT-qPCR or amount of infectious virus in the air between areas of primary and secondary occupancy within residences. Our work provides information about the presence of SARS-CoV-2 in the air within homes of individuals with COVID-19. Information herein can help individuals make informed decisions about personal exposure risks when sharing indoor spaces with infected individuals isolating at home and further inform health departments and the public about SARS-CoV-2 exposure risks within residences.

Pathogens can be collected from air and detected in samples by many methods. However, merely detecting pathogens does not answer whether they can spread disease. To fully assess health risks from exposure to airborne pathogens, the infectivity of those agents must be assessed. Air samplers which operate by growing particles through water vapor condensation and subsequently collecting them into a liquid medium have proven effective at conserving the viability of microorganisms. We present a study that assessed performance improvement of one such sampler, BioSpot-GEM, gained by augmenting it with an upstream virtual impactor (VI) designed to concentrate particles in aerosols. We demonstrate that such an integrated unit improved the collection of live by a median Concentration Factor ( ) of 1.59 and increased the recovery of viable human coronavirus OC43 (OC43) by a median of 12.7 as compared to the sampler without the VI. Our results also show that OC43 can be concentrated in this way without significant loss of infectivity. We further present that the small BioSpot-GEM bioaerosol sampler can collect live at an efficiency comparable to the larger BioSpot-VIVAS bioaerosol sampler. Our analyses show potential benefits toward improving the collection of viable pathogens from the air using a more portable water-based condensation air sampler while also highlighting challenges associated with using a VI with concentrated bioaerosols. This work can aid further investigation of VI usage to improve the collection of pathogens from air ultimately to better characterize health risks associated with airborne pathogen exposures.