Guide to industrial respiratory protection

Pritchard, James A.

doi:10.2172/7314909

Cited by 16 publications

(9 citation statements)

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“…Thus, the transfer rate from the hands to the attender's facial target membranes is λ 45 = (2 cm 2 ÷ 10 cm 2 ) × (0.083 min −1 ) × 0.35 = 5.8 × 10 −3 min −1 . The attender inhales at the rate of 0.020 m 3 min −1 , as does an individual performing light work, ( 32 ) for which λ 16 = (0.020 m 3 min −1 ) ÷ (64 m 3 ) = 3.1 × 10 −4 min −1 . Pathogens emitted in coughs are associated with aqueous particles containing salts and proteins, ( 21 ) which makes it likely that particle residues will adhere to surfaces and not be resuspended by casual contact; thus, we assume that λ 21 =λ 31 = 0.…”

Section: Methodsmentioning

confidence: 99%

Relative Contributions of Four Exposure Pathways to Influenza Infection Risk

2009

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The relative contribution of four influenza virus exposure pathways-(1) virus-contaminated hand contact with facial membranes, (2) inhalation of respirable cough particles, (3) inhalation of inspirable cough particles, and (4) spray of cough droplets onto facial membranes-must be quantified to determine the potential efficacy of nonpharmaceutical interventions of transmission. We used a mathematical model to estimate the relative contributions of the four pathways to infection risk in the context of a person attending a bed-ridden family member ill with influenza. Considering the uncertainties in the sparse human subject influenza dose-response data, we assumed alternative ratios of 3,200:1 and 1:1 for the infectivity of inhaled respirable virus to intranasally instilled virus. For the 3,200:1 ratio, pathways (1), (2), and (4) contribute substantially to influenza risk: at a virus saliva concentration of 10(6) mL(-1), pathways (1), (2), (3), and (4) contribute, respectively, 31%, 17%, 0.52%, and 52% of the infection risk. With increasing virus concentrations, pathway (2) increases in importance, while pathway (4) decreases in importance. In contrast, for the 1:1 infectivity ratio, pathway (1) is the most important overall: at a virus saliva concentration of 10(6) mL(-1), pathways (1), (2), (3), and (4) contribute, respectively, 93%, 0.037%, 3.3%, and 3.7% of the infection risk. With increasing virus concentrations, pathway (3) increases in importance, while pathway (4) decreases in importance. Given the sparse knowledge concerning influenza dose and infectivity via different exposure pathways, nonpharmaceutical interventions for influenza should simultaneously address potential exposure via hand contact to the face, inhalation, and droplet spray.

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Section: Methodsmentioning

confidence: 99%

Relative Contributions of Four Exposure Pathways to Influenza Infection Risk

2009

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“…We assume that an individual's breathing rate Q V is constant, and for the C. immitis example, Q V = 1.75 m 3 /hr. The latter value corresponds to a medium work rate, (2) and is higher than the typically assumed 1.0 m 3 /hr, which corresponds to a light work rate. Activities performed by individuals with the potential for C. immitis exposure (agricultural workers, construction workers) would be more rigorous than “light” work.…”

Section: Individual Riskmentioning

confidence: 95%

“…Respirators are most frequently worn against chemical toxicants in the form of vapors, gases, and nonviable aerosols. The general decision strategy for selecting respirators against chemicals is well established, (2–4) and although it has numerous steps, the overall idea is simple—one chooses a respirator predicted to keep the inspired level at or below the chemical's occupational exposure limit. Airborne pathogens are ignored in published decision strategies, (2–4) but the importance of selecting appropriate respirators is implicit in efforts by the Centers for Disease Control and Prevention to promote domestic preparedness against bioterrorism (5)…”

Section: Introductionmentioning

confidence: 99%

A Risk Analysis for Airborne Pathogens with Low Infectious Doses: Application to Respirator Selection Against Coccidioides immitis Spores

Nicas¹,

Hubbard²

2002

Risk Analysis

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Probability models incorporating a deterministic versus stochastic infectious dose are described for estimating infection risk due to airborne pathogens that infect at low doses. Such pathogens can be occupational hazards or candidate agents for bioterrorism. Inputs include parameters for the infectious dose model, distribution parameters for ambient pathogen concentrations, the breathing rate, the duration of an exposure period, the anticipated number of exposure periods, and, if a respirator device is used, distribution parameters for respirator penetration values. Application of the models is illustrated with a hypothetical scenario involving exposure to Coccidioides immitis, a fungus present in soil in areas of the southwestern United States Inhaling C. immitis spores causes a respiratory tract infection and is a recognized occupational hazard in jobs involving soil dust exposure in endemic areas An uncertainty analysis is applied to risk estimation in the context of selecting respiratory protection with a desired degree of efficacy.

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“…The first recorded use of a respirator was in the first century AD when Gaius Plinius Secundus, a Roman naturalist, suggested using animal bladder to protect Roman miners from inhaling lead oxide dust [ 29 ]. The prominent Leonardo da Vinci, in the 16th century, proposed using a wet cloth as a facial covering to protect against toxic chemicals [ 30 , 31 ]. Later, the industrial revolution in the early 1800s caused other environmental concerns that made more sophisticated respirators necessary [ 31 ].…”

Section: Historical Development Of Aerosols Face Protectionmentioning

confidence: 99%

Advanced Research and Development of Face Masks and Respirators Pre and Post the Coronavirus Disease 2019 (COVID-19) Pandemic: A Critical Review

Ogbuoji

Zaky²,

Escobar

2021

Polymers

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The outbreak of the COVID-19 pandemic, in 2020, has accelerated the need for personal protective equipment (PPE) masks as one of the methods to reduce and/or eliminate transmission of the coronavirus across communities. Despite the availability of different coronavirus vaccines, it is still recommended by the Center of Disease Control and Prevention (CDC), World Health Organization (WHO), and local authorities to apply public safety measures including maintaining social distancing and wearing face masks. This includes individuals who have been fully vaccinated. Remarkable increase in scientific studies, along with manufacturing-related research and development investigations, have been performed in an attempt to provide better PPE solutions during the pandemic. Recent literature has estimated the filtration efficiency (FE) of face masks and respirators shedding the light on specific targeted parameters that investigators can measure, detect, evaluate, and provide reliable data with consistent results. This review showed the variability in testing protocols and FE evaluation methods of different face mask materials and/or brands. In addition to the safety requirements needed to perform aerosol viral filtration tests, one of the main challenges researchers currently face is the inability to simulate or mimic true aerosol filtration scenarios via laboratory experiments, field tests, and in vitro/in vivo investigations. Moreover, the FE through the mask can be influenced by different filtration mechanisms, environmental parameters, filtration material properties, number of layers used, packing density, fiber charge density, fiber diameter, aerosol type and particle size, aerosol face velocity and concentration loadings, and infectious concentrations generated due to different human activities. These parameters are not fully understood and constrain the design, production, efficacy, and efficiency of face masks.

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Guide to industrial respiratory protection

Abstract: CHAPTER ONE. INTRODUCTION Background The (luide CHAPTER TWO. HISTORY OF RESPIRATORY PROTECTION CHAPTER THREE.

Cited by 16 publications

References 0 publications

Relative Contributions of Four Exposure Pathways to Influenza Infection Risk

Relative Contributions of Four Exposure Pathways to Influenza Infection Risk

A Risk Analysis for Airborne Pathogens with Low Infectious Doses: Application to Respirator Selection Against Coccidioides immitis Spores

Advanced Research and Development of Face Masks and Respirators Pre and Post the Coronavirus Disease 2019 (COVID-19) Pandemic: A Critical Review

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