scholarly journals Laboratory Study of Physical Barrier Efficiency for Worker Protection against SARS-CoV-2 while Standing or Sitting

2021 ◽  
Author(s):  
Jacob Bartels ◽  
Cheryl Fairfield Estill ◽  
I-Chen Chen ◽  
Dylan Neu
Keyword(s):  
Laboratory Study ◽  
Grocery Stores ◽  
Physical Barrier ◽  
Particle Count ◽  
Engineering Control ◽  
Transparent Barrier ◽  
Particle Counts ◽  
Barrier Efficiency ◽  
Number Of Particles ◽  
Nail Salons

Transparent barriers were installed as a response to the SARS-COV-2 pandemic in many customer-facing industries. Transparent barriers are an engineering control that are utilized to intercept air traveling between customers to workers. Information on the effectiveness of these barriers against aerosols is limited. In this study, a cough simulator was used to represent a cough from a customer. Two optical particle counters were used (one on each side of the barrier, labeled reference and worker) to determine the number of particles that migrated around a transparent barrier. Nine barrier sizes and a no barrier configuration were tested with six replicates each. Tests of these 10 configurations were conducted for both sitting and standing scenarios to represent configurations common to nail salons and grocery stores, respectively. Barrier efficiency was calculated using a ratio of the particle count results (reference/worker). Barriers had better efficiency when they were 9 to 39 cm (3.5 to 15.5 inches) above cough height and at least 91 cm (36 inches) wide, 92% and 93% respectively. Barriers that were 91 cm (36 inches) above table height for both scenarios blocked 71% or more of the particles between 0.35–0.725 µm and 68% for particles between 1 to 3 µm. A barrier that blocked an initial cough was effective at reducing particle counts. While the width of barriers was not as significant as height in determining barrier efficiency it was important that a barrier be placed where interactions between customers and workers are most frequent.

scholarly journals Ultra-high Cleanliness of ISO Class Minus 2 Realized by Clean-Unit System Platform for Integrating the Bottom-up and Top-down Systems

2013 ◽  
Vol 61 (2) ◽  
pp. 157-160
Author(s):  
Md Dalilur Rahaman ◽  
Hideo Kaiju ◽  
Akira Ishibashi
Keyword(s):  
Stainless Steel ◽  
Coming Out ◽  
Feedback Loop ◽  
High Efficiency ◽  
Top Down ◽  
Airborne Particle ◽  
Particle Count ◽  
Unit System ◽  
Better Than ◽  
Number Of Particles

The time dependence of the airborne particle count and the cleanliness of an airtight stainless steel clean-unit system platform (S-CUSP) with 100% air feedback through the feedback loop by installing the ultra low penetration air (ULPA) filter just beneath the high efficiency particulate air (HEPA) filter in the feedback loop has been studied. By controlling the number of particles coming out from the HEPA filter, the ultra high cleanliness of ISO class minus 2 has been obtained, which is five orders of magnitude better than that of the super cleanroom (ISO Class 3). Analyses of the experimental results demonstrate that the S-CUSP with flat feedback loop would be a viable economical means to achieve the more stringent cleanliness class, which has the immense importance for expediting the multi-disciplinary experiments and production fields such as nanotechnologies and biotechnologies. DOI: http://dx.doi.org/10.3329/dujs.v61i2.17063 Dhaka Univ. J. Sci. 61(2): 157-160, 2013 (July)

Monitoring for Cryptosporidium risk: do particle counters help?

2002 ◽  
Vol 2 (1) ◽  
pp. 171-180
Author(s):  
A. Morse ◽  
R. Wilson ◽  
A. Hull ◽  
J. Simms
Keyword(s):  
Loading Rate ◽  
Size Range ◽  
Raw Water ◽  
Water Turbidity ◽  
Particle Count ◽  
Water Particle ◽  
Increased Risk ◽  
Process Failure ◽  
Particle Counts ◽  
Clarified Water

Turbidity measurements are used extensively for monitoring water quality, and as a warning for process failure which may carry a risk of Cryptosporidium breakthrough. However, turbidity is most sensitive to particles in the submicrometre size range, whereas Cryptosporidium is 4-6 μm in diameter. The question therefore remains - do particle counters help in monitoring for the risk of Cryptosporidium breakthrough? A full year study was undertaken at a direct river abstraction works. The project aimed to establish whether particle counts can be used to predict an increased risk of Cryptosporidium breakthrough. Although protozoan (oo)cysts were often present in low numbers in the raw water, none was detected in the final water. Particle counts and turbidity measurements were carried out on three RGFs and the raw and clarified water. Online Cryptosporidium and Giardia samples were also taken daily from the three RGFs being monitored for particles, and bacteriological analyses were carried out on the same sample points. Other plant parameters and environmental factors were also monitored. Particle counts from RGFs varied significantly. The main factors influencing the filtered water particle count appeared to be raw water turbidity and algal counts, and the particulate loading rate to the filters.

Clarity Evaluation of Distilled Alcoholic Products with a Particle Counter

1976 ◽  
Vol 59 (3) ◽  
pp. 671-674
Author(s):  
Duane H Strunk ◽  
Bertha M Timmel ◽  
Arthur A Andreasen
Keyword(s):  
Particle Counter ◽  
Average Data ◽  
Apparent Relationship ◽  
Particle Counts ◽  
Number Of Particles

Abstract An HIAC particle counter is used to measure clarity of distilled alcoholic products. The number of particles is measured in 5 size ranges from 2 to 90 μm. Average data are given for whiskies, brandy, rum, white gin, and vodka. The highest counts are obtained for aged products and most of the particles are 2–5 μm. The particle counts of different brands of blended whiskies varied from 62 to 5265 particles/ml in the 2–90 μm range. There is no apparent relationship between nephelometer values and particle counts.

Cold Water Effects on Enhanced Coagulation of High DOC, Low Turbidity Water

2001 ◽  
Vol 36 (4) ◽  
pp. 701-717 ◽  
Author(s):  
Larry Braul ◽  
T. Viraraghavan ◽  
Darrell Corkal
Keyword(s):  
Aluminum Sulfate ◽  
Cold Water ◽  
Enhanced Coagulation ◽  
Treated Water ◽  
Particle Count ◽  
Water Particle ◽  
Residual Aluminum ◽  
Water Effects ◽  
Particle Counts ◽  
High Concentrations

Abstract Prairie farm reservoirs are usually low in turbidity and contain high concentrations of dissolved organic carbon (DOC). Some are treated with aluminum sulfate in late fall when the water drops below 3°C, often with poor turbidity reduction results. Jar tests using aluminum sulfate were conducted to study the effect of water temperature on enhanced coagulation of a typical high DOC prairie water. Jar tests showed that temperature affects turbidity, particle counts and total residual aluminum but does not affect DOC, UV254 absorbance and colour reduction. Turbidity of the treated water increased consistently as the temperature decreased. Particle counts in the 1 to 10 μm range were reduced by two logs at 20°C but only by one log at 1.5°C indicating inferior oocyst removal at low temperatures. Bentonite addition at 1.5°C did not affect the treated water particle counts but because the bentonite increased the raw water particle count, the reduction of the particles could be increased by one log. Coagulant demand for the water tested without pH adjustment is one to two mg Al per mg of DOC at all temperatures tested. The optimum pH for all temperatures was about 6.0 for DOC removal and about 6.5 for turbidity removal based on a dosage increment of 0.5 pH units. UV254 absorbance is well suited to predict optimum aluminum sulfate dosage for DOC removal.

Non-linear compartmental models

1984 ◽  
Vol 16 (1) ◽  
pp. 24-24
Author(s):  
M. J. Faddy
Keyword(s):  
Compartmental Model ◽  
Probability Distributions ◽  
Compartmental Analysis ◽  
Compartmental Models ◽  
General Will ◽  
Particle Count ◽  
Multinomial Probability ◽  
Model Independent ◽  
The Mean ◽  
Particle Counts

The linear compartmental model arises when ‘particles’ move independently between (or out of) a system of compartments in a stochastically similar way. With a given ‘initial’ particle count, the subsequent compartmental particle counts follow multinomial probability distributions (Faddy (1976)) for Markov or semi-Markov movement processes. One immediate consequence of this is that the variance of the compartmental particle count is always less than the mean, with the result that the coefficient of variation is very small for large mean counts. In applications (e.g, Faddy, Jones and Edwards (1976)) this underestimation of the variation can be a shortcoming of a compartmental analysis. Clustering, introduced by Matis and Wehrly (1981), where ‘clusters’ of particles may move together, is a way in which increased variability may be attained. Increased variability in general will result from relaxing the main assumption that gives rise to a linear model: independent behaviour of the particles. Such nonlinear compartmental models can be generally difficult to handle; in this paper some particular cases are discussed and illustrated with reference to one- and twocompartment systems.

scholarly journals Check the gap: Facemask performance and exhaled aerosol distributions around the wearer

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243885
Author(s):  
Emily L. Kolewe ◽  
Zachary Stillman ◽  
Ian R. Woodward ◽  
Catherine A. Fromen
Keyword(s):  
Social Distance ◽  
Material Characterization ◽  
Critical Element ◽  
Hygroscopic Growth ◽  
Particle Count ◽  
Industry Standard ◽  
3D Printed ◽  
Reproducible Method ◽  
Particle Counts

Current facemask research focuses on material characterization and efficiency; however, facemasks are often not tested such that aerosol distributions are evaluated from the gaps in the sides, bottom, and nose areas. Poor evaluation methods could lead to misinformation on optimal facemasks use; a high-throughput, reproducible method which illuminates the issue of fit influencing aerosol transmission is needed. To this end, we have created an in vitro model to quantify particle transmission by mimicking exhalation aerosols in a 3D printed face-nose-mouth replica via a nebulizer and quantifying particle counts using a hand-held particle counter. A sewn, sewn with pipe cleaner nose piece, and sewn with a coffee filter facemask were used to evaluate current common homemade sewn facemask designs, benchmarked against industry standard surgical, N95 respirator tightly fit, and N95 respirator loosely fit facemasks. All facemasks have significantly reduced particle counts in front of the facemask, but the side and top of the facemask showed increases in particle counts over the no facemask condition at that same position, suggesting that some proportion of aerosols are being redirected to these gaps. An altered size distribution of aerosols that escape at the vulnerable positions was observed; escaped particles have larger count median diameters, with a decreased ratio of smaller to larger particles, possibly due to hygroscopic growth or aggregation. Of the homemade sewn facemasks, the facemask with a coffee filter insert performed the best at reducing escaped aerosols, with increased efficiency also observed for sewn masks with a pipe cleaner nose piece. Importantly, there were minimal differences between facemasks at increasing distances, which supports that social distance is a critical element in reducing aerosol transmission. This work brings to light the importance of quantifying particle count in positions other than directly in front of the facemask and identifies areas of research to be explored.

scholarly journals Modelling effectiveness of PPE on aerosol exposure for healthcare workers during typical ENT procedures

2021 ◽  
Vol 4 (4) ◽  
pp. 24-29
Author(s):  
B.A. Senior ◽  
R.J. Schlosser ◽  
P.R. Lesch Jr.
Keyword(s):  
Healthcare Workers ◽  
Healthcare Providers ◽  
Protective Equipment ◽  
Test Model ◽  
Middle Meatus ◽  
Worst Case ◽  
Particle Count ◽  
Aerosol Exposure ◽  
Particle Counts ◽  
The Impact

BACKGROUND: Previous studies report environmental aerosolization with various endonasal procedures, but do not specifically measure intranasal levels of inhaled aerosolized particles in healthcare providers (HCP) performing such procedures. The purpose of this study is to measure the impact of various types of personal protective equipment (PPE) worn by HCP during a variety of office-based endonasal procedures. METHODOLOGY: Simulated sneeze and office-based procedures were performed in a test model and aerosol levels were quanti- fied in the middle meatus of a simulated HCP model wearing various forms of PPE by using a laser diode-based particle counter. Endoscopic exam, balloon sinus dilation, suction and irrigation, simulated tissue resection with a microdebrider, and routine debridement procedures were evaluated. The aerosol levels were evaluated with and without the use of PPE to assess HCP aerosol exposure. RESULTS: A simulated sneeze represents a worst-case aerosol generating event when compared to other common office-based procedures (approximately 1,000 times greater than baseline particle count). Common endoscopic procedures did not generate significantly greater particle counts above baseline. When compared to no mask, a surgical mask reduces particle counts experi- enced by HCP in the middle meatus by 69%, while an N95 mask significantly reduced particles by 93%. CONCLUSIONS: The levels of aerosols generated during common office-based procedures are consistent with the background aerosol levels measured at baseline. Masks are effective, with the N95 mask most effective at reducing HCP exposure to aerosols generated during a simulated sneeze.

scholarly journals Prediction of Particulate Contamination on an Aperture Window

1996 ◽  
Vol 39 (2) ◽  
pp. 42-48
Author(s):  
Aleck Lee ◽  
Michael Fong
Keyword(s):  
Light Scattering ◽  
Incident Light ◽  
Image Analyzer ◽  
Particulate Contamination ◽  
Flight Operations ◽  
Surface Particle ◽  
Particle Counts ◽  
Contaminant Distribution ◽  
Number Of Particles ◽  
Particulate Surface

This paper presents an analysis of light scattering by surface particles on the sensor window of a missile during ascent flight. The particulate contaminant distribution on the window is calculated by tallying the number of particles in a set of size ranges. The particulate contamination at the end of the mission is predicted by adding the contributions from the events of ground and flight operations. The surface particle redistribution caused by vibroacoustic-induced surface acceleration was found to contribute the most to particulate surface contamination. The analytical surface obscuration calculation with a set of particle counts was compared with the results of the image analyzer measurement. The analytical results, which were calculated with a given function of particle shape depending on size, were more conservative than the measurement. A scattering calculation using a verified BSDF model showed that the scattering was less than 0.001 at 20 deg off the direction of the incident light in the mid IR wavelength when the surfaces were at Level 300 initially.

scholarly journals Fallow time determination in dentistry using aerosol measurement

2021 ◽  
Author(s):  
Shakeel Shahdad ◽  
Annika Hindocha ◽  
Tulsi Patel ◽  
Neil Cagney ◽  
Jens-Dominik Mueller ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Natural Ventilation ◽  
High Efficiency ◽  
High Volume ◽  
Mechanically Ventilated ◽  
Particle Count ◽  
Mitigating Factors ◽  
Particle Counts ◽  
Particle Sizer

AbstractAimTo calculate fallow time (FT) required following dental aerosol generating procedures (AGPs) in both a dental hospital (mechanically ventilated) and primary care (non-mechanically ventilated). Secondary outcomes were to identify spread and persistence of aerosol in open clinics compared to closed surgeries (mechanically ventilated environment), and identify if extra-oral scavenging (EOS) reduces production of aerosol and FT.MethodsIn vitro simulation of fast handpiece (FHP) cavity preparations using a manikin was conducted in a mechanically and non-mechanically ventilated environment using Optical Particle Sizer™ and NanoScan™ at baseline, during the procedure and fallow period.ResultsAGPs carried out in the non-mechanically, non-ventilated environment failed to achieve baseline particle levels after one hour. In contrast, when windows were opened after AGP, there was an immediate reduction in all particle sizes.In mechanically ventilated environments the baseline levels of particles were very low and particle count returned to baseline within 10 minutes following AGP. There was no detectable difference between particles in mechanically ventilated open bays and closed surgeries.The effect of the EOS was greater in non-mechanically ventilated environment on reducing the particle count; additionally, it also reduced the spikes in particle counts in mechanically ventilated environments.ConclusionHigh-efficiency particulate air filtered mechanical ventilation along with mitigating factors (high-volume suction) resulted in reduction of FT (10 minutes). Non-ventilated rooms failed to reach baseline level even after one hour of FT. There was no difference in particle counts in open bay or closed surgeries in mechanically ventilated settings. The use of an EOS device can reduce the particulate spikes during procedures in both mechanical and non-mechanical environments.This study confirms that AGPs are not recommended in dental surgeries where no ventilation is possible. No difference was demonstrated in FT required in open bays and closed surgeries in mechanically ventilated settings.Clinical significanceAGPs should not be carried out in surgeries where ventilation is not possible. Mechanical ventilation for AGPs should be gold standard; where not available or practical then the use of natural ventilation with EOS helps reduce FT. AGPs can be carried out in open bay environment with a minimum of 6 air changes per hour of mechanical ventilation. Four-handed dentistry with high-volume suction and saliva ejector are essential mitigating factors during AGPs.

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