scholarly journals Separation and Disinfection of Contagious Aerosols from the Perspective of SARS-CoV-2

Separations ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 190
Author(s):  
J. J. H. Brouwers
Keyword(s):  
Indoor Air ◽  
Service Time ◽  
Particle Number ◽  
Random Distribution ◽  
Particle Removal ◽  
Virus Particles ◽  
Number Distribution ◽  
Clean Air ◽  
Particle Separator ◽  
Droplet Nuclei

An assessment was performed on methods of separating and disinfecting airborne droplet nuclei containing viruses, such as SARS-CoV-2. The droplet nuclei originate from evaporating aerosols emitted by the coughing, singing, sneezing, etc. of infected humans. Based on empirical data and theoretical analysis, we successively determined: (i) the particle number distribution of nuclei versus the nucleus diameter, (ii) the statistical distribution of the viral content in the droplet nuclei starting from a uniform random distribution of viruses in the mucus, (iii) the particle number distribution of droplet nuclei containing at least one virus particle, and (iv) the effectiveness of methods for removing and disinfecting nuclei containing one or more virus particles from indoor air; viz., ventilation with fresh air, filtering with porous media, such as HEPA, and centrifugal separation and simultaneous disinfection, particularly with a rotational particle separator (RPS). Indoor aerosol removal with RPS supplemented with HEPA to arrest tiny volumes of very small particles was found to be the most effective. It is as good as particle removal through ventilation with clean air over long periods of time. An RPS facilitates direct elimination of viruses in the collected nuclei by flushing with a disinfection liquid. The components of an RPS are recyclable. Combining HEPA with an RPS extends the service time of HEPA by almost two orders of magnitude compared to the relatively short service time of stand-alone HEPA filters.

Influence of particle size and operating parameters on virus ultrafiltration efficiency

2011 ◽  
Vol 11 (1) ◽  
pp. 31-38
Author(s):  
Angayar K. Pavanasam ◽  
Ali Abbas ◽  
Vicki Chen
Keyword(s):  
Particle Size ◽  
Filtration Efficiency ◽  
Transmembrane Pressure ◽  
Operating Parameters ◽  
Particle Removal ◽  
Major Step ◽  
Virus Removal ◽  
Virus Particles ◽  
Key Factor ◽  
Effect Of Particle Size

In water treatment, virus removal using ultrafiltration is a major step towards better water quality. In this paper, we study virus filtration efficiency using surrogate virus particles and via statistical surface-response approach. We focus on the effect of particle size (20–100 nm range) as a key factor along with the effects of transmembrane pressure (20–60 kPa range) and feed flowrate (0.3–1.0 L/F;min range) on the filtration virus removal efficiency (LRV). The particle size is shown to impart a great deal of influence on surrogate particle removal. The effect of particle-to-pore-size ratio is reported for comparison of membrane molecular weight cut off (MWCO) performance. It was shown experimentally and through the developed empirical regression model that transmembrane pressure plays a major role in controlling the filtration efficiency along with flowrate. In the studied experimental range, higher LRV values are obtained at lower transmembrane pressure (20 kPa) and at higher feed flowrate (1 L/F;min). Further the effect on LRV of the interaction between transmembrane pressure and particle size seems to be more significant than that of the interaction of flowrate with particle size.

scholarly journals Response of particle number concentrations to Clean Air Action: Lessons from the first long-term aerosol measurements in a typical urban valley, West China

2021 ◽  
Author(s):  
Suping Zhao ◽  
Ye Yu ◽  
Jianglin Li ◽  
Daiying Yin ◽  
Shaofeng Qi ◽  
...  
Keyword(s):  
Particle Number ◽  
Size Range ◽  
Transport Processes ◽  
Control Measures ◽  
Effective Control ◽  
Chinese Government ◽  
In Situ Observation ◽  
Haze Pollution ◽  
Clean Air

Abstract. The strictest ever Clean Air Action (CAA) has been implemented by Chinese government since 2013 to alleviate the severe haze pollution. The PM2.5 mass concentration was found to be largely reduced in response to emission mitigation policies, but response of particle number concentrations (PNCs) to CAA was less evaluated in the previous studies, which may be largely different from PM2.5 mass due to newly formed particle impacts. In this work, the first in-situ observation of particle number size distributions (PNSDs) during 2012–2019 in urban Lanzhou was used to analyze long-term PNCs variations and CAA impacts. The average number of particles in nucleation (N13–25, particle number in the size range of 13–25 nm), Aitken (N25–100, particle number in the size range of 25–100 nm) and accumulation (N100–800, particle number in the size range of 100–800 nm) modes were respectively 2514.0 cm−3, 10768.7 cm−3, and 3258.4 cm−3, and N25–100 accounted for about 65.1 % of total PNCs during the campaign. K-means clustering technique was used to classify the hourly mean PNSDs into six clusters, and each cluster corresponded to a specific source and influencing factor. The polluted clusters governed the winter PNCs before 2016, and their occurrence was less and less frequent after 2016, which was largely dominated by reduction in primary emissions. However, the contribution of new particle formation (NPF) events to summer N13–25 decreased from 50 % to about 10 % during 2013 to 2015, and then increased to reach around 60 % in 2019. The trends of size-resolved PNCs for each cluster were quantified by Theil-Sen regression. The size-segregated PNCs exhibited downward trends for all clusters during 2012–2015, especially in spring. The annual relative slopes of spring PNCs varied from −54.7 % to −17.2 %, −42.6 % to −14.1 %, and −40.7 % to −17.5 % per year for 13–25, 25–100, and 100–800 nm size ranges, and the reduction in the polluted clusters was much larger than NPF clusters. The ultrafine particle number was increased and the amplitude was much greater during 2016–2019. The annual relative slopes of N13–25 varied between 8.0 % in fall and 135.5 % in spring for NPF cluster. In response to CAA, the increased daytime net radiation, higher ambient temperature and lower relative humidity at noon for NPF events also could partly explain the higher N13–25 induced by the more frequent nucleation events after 2016, especially in spring. The air mass were mainly from the adjacent regions of urban Lanzhou and less affected by long-range transport for NPF events, and the thus particles were not easily grown by coagulation during transport processes, which was helpful for occurrence of NPF events. Therefore, some effective control measures cooperatively controlled particle number and mass should be took for the Chinese megacities.

scholarly journals Creating Clean Air Spaces During Wildland Fire Smoke Episodes: Web Summit Summary

2021 ◽  
Vol 9 ◽  
Author(s):  
Gilliane Davison ◽  
Karoline K. Barkjohn ◽  
Gayle S. W. Hagler ◽  
Amara L. Holder ◽  
Sarah Coefield ◽  
...  
Keyword(s):  
Public Health ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Wildland Fire ◽  
Air Filtration ◽  
Wildfire Smoke ◽  
Fire Smoke ◽  
Clean Air ◽  
Pollution Events

Effective strategies to reduce indoor air pollutant concentrations during wildfire smoke events are critically needed. Worldwide, communities in areas prone to wildfires may suffer from annual smoke exposure events lasting from days to weeks. In addition, there are many areas of the world where high pollution events are common and where methods employed to reduce exposure to pollution may have relevance to wildfire smoke pollution episodes and vice versa. This article summarizes a recent virtual meeting held by the United States Environmental Protection Agency (EPA) to share research, experiences, and other information that can inform best practices for creating clean air spaces during wildland fire smoke events. The meeting included presentations on the public health impacts of wildland fire smoke; public health agencies' experiences and resilience efforts; and methods to improve indoor air quality, including the effectiveness of air filtration methods [e.g., building heating ventilation and air conditioning (HVAC) systems and portable, free-standing air filtration systems]. These presentations and related research indicate that filtration has been demonstrated to effectively improve indoor air quality during high ambient air pollution events; however, several research questions remain regarding the longevity and maintenance of filtration equipment during and after smoke events, effects on the pollution mixture, and degree to which adverse health effects are reduced.

scholarly journals Efficiency of an Air Cleaner Device in Reducing Aerosol Particulate Matter (PM) in Indoor Environments

2019 ◽  
Vol 17 (1) ◽  
pp. 18 ◽  
Author(s):  
Paola Fermo ◽  
Valeria Comite ◽  
Luigi Falciola ◽  
Vittoria Guglielmi ◽  
Alessandro Miani
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Particle Number ◽  
Indoor Environments ◽  
Aerodynamic Diameter ◽  
Healthy Environment ◽  
Household Environment ◽  
Commercial Device

Indoor air quality (IAQ) in household environments is mandatory since people spend most of their time in indoor environments. In order to guarantee a healthy environment, air purification devices are often employed. In the present work, a commercial household vacuum cleaner has been tested in order to verify its efficiency in reducing the mass concentration and particle number of aerosol particulate matter (PM). The efficiency has been tested measuring, while the instrument was working, PM10 (particles with aerodynamic diameter less than 10 μm), PM2.5 (particles with aerodynamic diameter less than 2.5 μm), PM1 (particles with aerodynamic diameter less than 1 μm), and 7 size-fractions in the range between 0.3 and >10 μm. Measurements have been carried out by means of a portable optical particle counter instrument and simulating the working conditions typical of a household environment. It has been found that the tested commercial device significantly reduces both PM concentrations and particle number, especially in the finest fraction, i.e., particles in the range 0.3–0.5 μm, allowing an improvement of indoor air quality.

scholarly journals Reaerosolization of MS2 Bacteriophage from an N95 Filtering Facepiece Respirator by Simulated Coughing

2011 ◽  
Vol 56 (3) ◽  
pp. 315-325 ◽  
Author(s):  
Edward M. Fisher ◽  
Aaron W. Richardson ◽  
Shannon D. Harpest ◽  
Kent C. Hofacre ◽  
Ronald E. Shaffer
Keyword(s):  
Peak Flow ◽  
Respiratory Viruses ◽  
Risk Assessments ◽  
Andersen Cascade Impactor ◽  
Virus Particles ◽  
Healthcare Settings ◽  
Bacteriophage Ms2 ◽  
Exposure Data ◽  
Pathogenic Viruses ◽  
Droplet Nuclei

Abstract The supply of N95 filtering facepiece respirators (FFRs) may not be adequate to match demand during a pandemic outbreak. One possible strategy to maintain supplies in healthcare settings is to extend FFR use for multiple patient encounters; however, contaminated FFRs may serve as a source for the airborne transmission of virus particles. In this study, reaerosolization of virus particles from contaminated FFRs was examined using bacteriophage MS2 as a surrogate for airborne pathogenic viruses. MS2 was applied to FFRs as droplets or droplet nuclei. A simulated cough (370 l min−1 peak flow) provided reverse airflow through the contaminated FFR. The number and size of the reaerosolized particles were measured using gelatin filters and an Andersen Cascade Impactor (ACI). Two droplet nuclei challenges produced higher percentages of reaerosolized particles (0.21 and 0.08%) than a droplet challenge (<0.0001%). Overall, the ACI-determined size distribution of the reaerosolized particles was larger than the characterized loading virus aerosol. This study demonstrates that only a small percentage of viable MS2 viruses was reaerosolized from FFRs by reverse airflow under the conditions evaluated, suggesting that the risks of exposure due to reaerosolization associated with extended use can be considered negligible for most respiratory viruses. However, risk assessments should be updated as new viruses emerge and better workplace exposure data becomes available.

Radon and its decay products in an air-conditioned auditorium in correlation with indoor air parameters

2016 ◽  
Vol 26 (5) ◽  
pp. 621-630 ◽  
Author(s):  
Bernard Polednik ◽  
Krzysztof Kozak ◽  
Jadwiga Mazur ◽  
Marzenna Dudzińska ◽  
Dominik Grządziel
Keyword(s):  
Indoor Air ◽  
Air Conditioning ◽  
Particle Number ◽  
Decay Product ◽  
Significant Negative Correlation ◽  
Particle Mass ◽  
Average Particle ◽  
Air Conditioning System ◽  
Decay Products ◽  
The Impact

The measurements of radon and its attached decay product activity concentrations were carried out in an occupied and unoccupied auditorium during three air-conditioning modes i.e. air-conditioning system switched off (air-conditioning off), air-conditioning system switched off during the night and switched on during the day (air-conditioning on/off) and air-conditioning system switched on (air-conditioning on). Higher average concentrations of radon and its decay products were recorded in the auditorium when the air-conditioning system was switched off. The average particle mass and CO2 concentrations and indoor air thermal parameters were elevated during the air-conditioning on/off mode. A statistically significant ( p < 0.001) positive correlation between the decay product concentrations and the particle number and average particle mass concentrations has been observed in the air-conditioning off mode ( r = 0.55 and r = 0.68) and in the air-conditioning on/off mode ( r = 0.54 and r = 0.62, respectively). A significant negative correlation has been observed between the decay product concentrations and the indoor air temperature and CO2 concentrations in the air-conditioning off mode ( r = −0.86 and r = −0.47, respectively). The obtained results confirmed the impact of the air-conditioning system operation on the decrease of health risks related to the presence of radon and its decay products in air conditioned premises.

scholarly journals Effects of Air Purifiers on the Spread of Simulated Respiratory Droplet Nuclei and Virus Aggregates

2021 ◽  
Vol 18 (16) ◽  
pp. 8426
Author(s):  
Ki Joon Heo ◽  
Inyong Park ◽  
Gunhee Lee ◽  
Keejung Hong ◽  
Bangwoo Han ◽  
...  
Keyword(s):  
Particle Number ◽  
Test Chamber ◽  
Number Concentration ◽  
Deionized Water ◽  
Continuous Operation ◽  
Polystyrene Latex ◽  
Airborne Particles ◽  
Particle Number Concentration ◽  
Air Purifier ◽  
Droplet Nuclei

The present study was performed to quantitatively evaluate the effects of air purifiers on the spread of COVID-19 and to suggest guidelines for their safe use. To simulate respiratory droplet nuclei and nano-sized virus aggregates, deionized water containing 100 nm of polystyrene latex (PSL) particles was sprayed using a vibrating mesh nebulizer, and the changes in the particle number concentration were measured for various locations of the particle source and air purifier in a standard 30 m3 test chamber. The spread of the simulated respiratory droplet nuclei by the air purifier was not significant, but the nano-sized aggregates were significantly affected by the airflow generated by the air purifier. However, due to the removal of the airborne particles by the HEPA filter contained in the air purifier, continuous operation of the air purifier reduced the number concentration of both the simulated respiratory droplet nuclei and nano-sized aggregates in comparison to the experiment without operation of the air purifier. The effect of the airflow generated by the air purifier on the spread of simulated respiratory droplet nuclei and nano-sized aggregates was negligible when the distance between the air purifier and the nebulizer exceeded 1 m.

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