The Effectiveness of Air Ionization in Reducing Bioaerosols and Airborne PRRS Virus in a Ventilated Space

2019 ◽  
Vol 62 (5) ◽  
pp. 1299-1314
Author(s):  
Amy La ◽  
Qiang Zhang ◽  
David B. Levin ◽  
Kevin M. Coombs
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Removal Efficiency ◽  
Geometric Mean ◽  
Ventilation Rate ◽  
Aerosol Concentration ◽  
Respiratory Syndrome Virus ◽  
Airflow Rate ◽  
Air Ionization ◽  
Concentration Changes

Abstract. The presence of bioaerosols in swine production facilities affects the respiratory health of swine workers and pigs. Air ionization (AI) is an affordable technology for removing bioaerosols in the air. The purpose of this study was to assess the effect of AI on aerosols in a ventilated space in terms of reduction in aerosol concentration, changes in particle size distribution, and reduction of airborne Porcine Reproductive and Respiratory Syndrome virus (PRRSV). Experiments were performed in a two-chamber system in which aerosols containing PRRSV were introduced. Tests were conducted for two ventilation rates of 34 and 136 m3 h-1 and two aerosol generation rates of 14.8 and 33.0 mL h-1. The aerosol concentration and size distribution were measured with an aerosol particle size spectrometer. The average reduction in geometric mean diameter of aerosols by AI treatment ranged from 8% to 53%, and reduction in aerosol concentration ranged from 68% to 96%. Ventilation rate was found to affect the efficiency of AI in reducing aerosol concentration; the removal efficiency decreased with increased ventilation rate. The removal efficiency of AI varied with particle size. Specifically, at the low airflow rate, the removal efficiency of AI increased sharply with particle size from 70% at 0.25 µm to 95% at 0.6 µm and reached 100% for particles larger than 6 µm. At the high airflow rate, the removal efficiency varied between 50% to 80% before reaching 100% removal for particles sizes of 7 to 9 µm. The average reduction in PRRSV concentration ranged from 68% to 96%, and the residual PRRSV remaining in the air after treatment ranged from 154 to 4593 viral genome copy number (VGCN) m-3. Ozone generation by the AI system was not measured in this study, and it may be a concern due to the health risk to pigs and workers when using AI systems for removing bioaerosols. Keywords: Air ionization, Air quality, Bioaerosols, Porcine Reproductive and Respiratory Syndrome Virus, Swine.

scholarly journals Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

2016 ◽  
Vol 113 (50) ◽  
pp. 14243-14248 ◽  
Author(s):  
Kamal Kant Chandrakar ◽  
Will Cantrell ◽  
Kelken Chang ◽  
David Ciochetto ◽  
Dennis Niedermeier ◽  
...  
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Aerosol Concentration ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Moist Convection ◽  
Concentration Changes ◽  
Precipitation Formation

The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc<τt) for high aerosol concentration, and slow microphysics (τc>τt) for low aerosol concentration; here, τc is the phase-relaxation time and τt is the turbulence-correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs−1=τc−1+τt−1, and the measurements are in excellent agreement with this finding. The result underscores the importance of droplet size dispersion for aerosol indirect effects: increasing aerosol concentration changes the albedo and suppresses precipitation formation not only through reduction of the mean droplet diameter but also by narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol/slow microphysics limit are likely of leading importance for precipitation formation.

Determination of Particle-Size Distribution and Concentration of Cigarette Smoke by a Light-Scattering Method

1977 ◽  
Vol 9 (3) ◽  
Author(s):  
T. Okada ◽  
Y. Ishizu ◽  
K. Matsunuma
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cigarette Smoke ◽  
Scattered Light ◽  
Geometric Mean ◽  
Number Concentration ◽  
Scattering Method ◽  
Working Standard

AbstractA new method for determining particle-size distribution of cigarette smoke particles was developed by simultaneous measurement of scattered light at three angles for a fixed wavelength. A theoretical chart useful for this purpose, which was made of the relative intensities of scattered light at the angles 45° and 135° to that at the angle 90°, was calculated on the basis of the Mie theory. The number concentration was determined from the Rayleigh ratio using the working standard method. The measurements were rapidly performed, without change of particle size during measuring time, with a device for dilution. The geometric mean diameter, the logarithmic standard deviation and the number concentration of mainstream smoke were found to be about 0.18 um, 0.4 and 3 X 10

Reconstructed expression for aerosol extinction coefficient by considering mass extinction efficiency and hygroscopic growth for polydipersed aerosol

2020 ◽  
Author(s):  
Chang Hoon Jung ◽  
JiYi Lee ◽  
Junshik Um ◽  
Yong Pyo Kim
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Growth Factor ◽  
Size Distribution ◽  
Enhancement Factor ◽  
Size Range ◽  
Geometric Mean ◽  
Mie Theory ◽  
Hygroscopic Growth ◽  
Particle Size Range

&lt;p&gt;In this study, simplified analytic type of expression for size dependent MEs (Mass efficiencies) are developed. The entire size was considered assuming lognormal size distribution for sulfate, nitrate and NaCl aerosol species and the MEE of each aerosol chemical composition was estimated by fitting Mie&amp;#8217;s calculation. The obtained results are compared with the results from the Mie-theory-based calculations and showed comparable results.&lt;/p&gt;&lt;p&gt;The mass efficiencies of all aerosol components for each size range are compared with Mie&amp;#8217;s results and approximated as a function of geometric mean diameter in the form of a power law formula. Finally, harmonic mean type approximation was used to cover entire particle size range.&lt;/p&gt;&lt;p&gt;Also, analytic expression of approximated scattering enhancement factor which stands for the effect of hygroscopic growth factor for polydispersed aerosol on aerosol optical properties are obtained.&lt;/p&gt;&lt;p&gt;Based on aerosol thermodynamic models, mass growth factor can be obtained and their optical properties can be obtained by using Mie theory with different aerosol properties and size distribution. Finally, scattering enhancement factor was approximated fRH for polydispersed aerosol as a function of RH.&lt;/p&gt;&lt;p&gt;Finally, we also compared the simple forcing efficiency (SFE, W/g) of polydisperse aerosols between the developed simple approach and by the method using the Mie theory. The results show that current obtained approximated methods are comparable with existing numercal calculation based results for polydipersed particle size.&lt;/p&gt;

scholarly journals Granulometric Characterization and Alteration during Composting of Industrial Cork Residue for Use as a Growing Medium

HortScience ◽  
2003 ◽  
Vol 38 (6) ◽  
pp. 1242-1246 ◽  
Author(s):  
E. Carmona ◽  
J. Ordovás ◽  
M.T. Moreno ◽  
M. Avilés ◽  
M.T. Aguado ◽  
...  
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Size Distribution ◽  
Geometric Mean ◽  
Quercus Suber ◽  
Growing Medium

This work describes the granulometry of industrial cork residue (bark of Quercus suber L.) and its possible alteration during composting to eliminate the high content of phytotoxic substances. Because of the differences in density of the different-sized cork particles, expression of the granulometric distribution in relation to volume reflected the size distribution more accurately than its expression in relation to weight. As a consequence, predictions of the physical and hydrological behavior of the substrate, deduced from its granulometry, were more accurate when this was calculated in relation to volume. Objective parameters used for textural comparison, such as the geometric mean (dg) and standard deviation of particle size (σg), which were previously used in soils, were tested. These permit the estimation of small differences in the particle size of different lots or the granulometric alteration occurring during composting. With the same purpose, a new diagram of textures for the classification of granular substrates was also studied.

Cleanroom Mats: An Investigation of Particle Removal

1996 ◽  
Vol 39 (4) ◽  
pp. 19-27
Author(s):  
W. Whyte ◽  
T. Shields ◽  
T. Prvan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Removal Efficiency ◽  
Adhesive Strength ◽  
Particle Removal ◽  
High Concentration ◽  
Low Concentration

The variables that influence the particle removal efficiency of cleanroom mats were investigated. The removal efficiency was generally found to be greater if the mat was of a softer type, the particles smaller, the particle size distribution more homogeneous, the distance between the particles greater, and the adhesive strength of the mat surface greater. One application of a mat surface was sufficient to remove a low concentration of similarly sized particles from a surface but it could require up to four mat surfaces to remove a high concentration of heterogeneously sized particles. It was found with heterogeneously sized particles that larger particles were removed first, thus allowing access to the smaller particles which could then be removed. If the mat was soft, it allowed larger particles to sink into it and smaller particles than normal to be picked up.

Size Distributions of Particles Extracted from Different Materials Compared with the MIL-STD-1246 Particle Size Distribution

2000 ◽  
Vol 43 (4) ◽  
pp. 25-29
Author(s):  
Roger Welker
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Geometric Mean ◽  
Industrial Applications ◽  
Distribution Analysis ◽  
Size Distributions ◽  
Naturally Occurring ◽  
History Of ◽  
Log Normal

MIL-STD-1246 particle-size distribution is the basis for specifying the particle cleanliness of surfaces for many governmental and industrial applications. MIL-STD-1246 states that naturally occurring particle contamination on surfaces follows a log-normal particle-size distribution, with a geometric mean of 1 μm, following a very precise size specification. However, the naturally occurring particle-size distribution may be a function of the material under examination or the prior cleaning or surface treatment history of the material. This paper explores the relation between the MIL-STD-1246 particle-size distribution and particle-size distributions measured after extraction followed by liquidborne particle-size distribution analysis.

scholarly journals Application of Multistep Inversion Method for Online Monitoring Aerosol Particle Size Distribution and Aerosol Concentration

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhenzong He ◽  
Liang Xu ◽  
Junkui Mao ◽  
Xingsi Han ◽  
Biao Zhang
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Sampling Time ◽  
Aerosol Concentration ◽  
Inversion Method ◽  
Time Interval ◽  
Aerosol Particle Size ◽  
Sampling Time Interval

Aerosol concentration in the flow is usually time varying, and aerosol particle size distribution (PSD) is considered to be unchanged, which increases the difficulty of the measurement of aerosol PSD and concentration online. To solve these problems, a kind of multistep inversion method based on the angular light-scattering (ALS) signals is proposed. First, the aerosol PSD is estimated using shuffled frog-leaping algorithms (SFLAs) from relative ALS signals. Then, with aerosol PSD as priori information, the aerosol concentration is obtained by the Kalman filter (KF) algorithm, widely used in the real-time control system of industrial facilities for its ability of fast predictions. The result reveals that the performance of the improved SFLA is better than that of the original SFLA in solving the aerosol PSD. Moreover, in studying the aerosol concentration, more accurate results can be obtained with larger standard deviation of process noise or smaller standard deviation of measurement noise, while decreasing sampling time interval can improve the accuracy of retrieval results and reduce time delay to a certain degree. So, to improve retrieval accuracy, the noise should be controlled, and appropriate sampling time interval should be selected. All the numerical simulations confirm that the methodology provides effective and reliable results in real-time estimating.

scholarly journals Particle-Size Distribution Models for the Conversion of Chinese Data to FAO/USDA System

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Wei Shangguan ◽  
YongJiu Dai ◽  
Carlos García-Gutiérrez ◽  
Hua Yuan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Soil Texture ◽  
Texture Classification ◽  
Geometric Mean ◽  
Coefficient Of Determination ◽  
Logistic Growth ◽  
United States Department ◽  
Data Points

We investigated eleven particle-size distribution (PSD) models to determine the appropriate models for describing the PSDs of 16349 Chinese soil samples. These data are based on three soil texture classification schemes, including one ISSS (International Society of Soil Science) scheme with four data points and two Katschinski’s schemes with five and six data points, respectively. The adjusted coefficient of determinationr2, Akaike’s information criterion (AIC), and geometric mean error ratio (GMER) were used to evaluate the model performance. The soil data were converted to the USDA (United States Department of Agriculture) standard using PSD models and the fractal concept. The performance of PSD models was affected by soil texture and classification of fraction schemes. The performance of PSD models also varied with clay content of soils. The Anderson, Fredlund, modified logistic growth, Skaggs, and Weilbull models were the best.

scholarly journals Particle size distributions from laboratory-scale biomass fires using fast response instruments

2010 ◽  
Vol 10 (16) ◽  
pp. 8065-8076 ◽  
Author(s):  
S. Hosseini ◽  
Q. Li ◽  
D. Cocker ◽  
D. Weise ◽  
A. Miller ◽  
...  
Keyword(s):  
United States ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Geometric Mean ◽  
The United States ◽  
Biomass Combustion ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Mean Diameter

Abstract. Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in well controlled repeatable lab scale biomass fires for southwestern United States fuels with focus on chaparral. The combustion laboratory at the United States Department of Agriculture-Forest Service's Fire Science Laboratory (USDA-FSL), Missoula, MT provided a repeatable combustion and dilution environment ideal for measurements. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which is attributable to dilution of the fresh smoke. Comparing mass size distribution from FMPS and APS measurement 51–68% of particle mass was attributable to the particles ranging from 0.5 to 10 μm for PM10. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most fuels produced a unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering) could be better distinguished using the slopes in MCE (Modified Combustion Efficiency) vs. geometric mean diameter than only using MCE values.

scholarly journals Evolution of Aerosol Particles in the Rainfall Process via Method of Moments

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Fangyang Yuan ◽  
Fujun Gan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Method Of Moments ◽  
Particle Number ◽  
Aerosol Particles ◽  
Geometric Mean ◽  
Number Concentration ◽  
Brownian Diffusion ◽  
Particle Number Concentration

The method of moments is employed to predict the evolution of aerosol particles in the rainfall process. To describe the dynamic properties of particle size distribution, the population balance equation is converted to moment equations by the method of moments and the converted equations are solved numerically. The variations of particle number concentration, geometric mean diameter, and geometric standard deviation are given in the cases that the Brownian diffusion and inertial impaction of particles dominate, respectively. The effects of raindrop size distribution on particle size distribution are analyzed in nine cases. The results show that the particle number concentration decreases as time goes by, and particles dominated by Brownian diffusion are removed more significantly. The particle number concentration decreases much more rapidly when particle geometric mean diameter is smaller, and the particle size distribution tends to be monodisperse. For the same water content, the raindrops with small geometric mean diameters can remove particles with much higher efficiency than those with large geometric mean diameters. Particles in the “Greenfield gap” are relatively difficult to scavenge, and a new method is needed to remove it from the air.

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