Removal of exhaled particles by ventilation and deposition in a multibed airborne infection isolation room

Qian, Hua; Li, Yuguo

doi:10.1111/j.1600-0668.2010.00653.x

Cited by 122 publications

(118 citation statements)

References 21 publications

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“…This is consistent with modeling results reported by Knibbs et al, (28) although they and other authors also found that the configuration and direction of the ventilation system, and other factors, can have a large impact on exposure and that these factors are difficult to predict and control. (17,29,30) In a similar manner to the time scale discussion above, our results show that ventilation has a much greater effect on exposure over the long term than in the short period immediately after a cough.…”

Section: Discussionsupporting

confidence: 69%

“…In two studies, Qian et al (16,17) placed manikins in a mock hospital ward and airborne isolation room and showed that the air jet from patient exhalation, airflows from the ventilation system, and respiratory activities of other individuals in the room interact to distribute aerosol particles. They also found that exhaled jets can travel long distances in some cases, and that commonly used room ventilation schemes are not effective at removing all sizes of aerosol particles.…”

Section: Introductionmentioning

confidence: 99%

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Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Lindsley

King

Thewlis

et al. 2012

Journal of Occupational and Environmental Hygiene

102

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Few studies have quantified the dispersion of potentially infectious bioaerosols produced by patients in the health care environment and the exposure of health care workers to these particles. Controlled studies are needed to assess the spread of bioaerosols and the efficacy of different types of respiratory personal protective equipment (PPE) in preventing airborne disease transmission. An environmental chamber was equipped to simulate a patient coughing aerosol particles into a medical examination room, and a health care worker breathing while exposed to these particles. The system has three main parts: (1) a coughing simulator that expels an aerosol-laden cough through a head form; (2) a breathing simulator with a second head form that can be fitted with respiratory PPE; and (3) aerosol particle counters to measure concentrations inside and outside the PPE and at locations throughout the room. Dispersion of aerosol particles with optical diameters from 0.3 to 7.5 μm was evaluated along with the influence of breathing rate, room ventilation, and the locations of the coughing and breathing simulators. Penetration of cough aerosol particles through nine models of surgical masks and respirators placed on the breathing simulator was measured at 32 and 85 L/min flow rates and compared with the results from a standard filter tester. Results show that cough-generated aerosol particles spread rapidly throughout the room, and that within 5 min, a worker anywhere in the room would be exposed to potentially hazardous aerosols. Aerosol exposure is highest with no personal protective equipment, followed by surgical masks, and the least exposure is seen with N95 FFRs. These differences are seen regardless of breathing rate and relative position of the coughing and breathing simulators. These results provide a better understanding of the exposure of workers to cough aerosols from patients and of the relative efficacy of different types of respiratory PPE, and they will assist investigators in providing research-based recommendations for effective respiratory protection strategies in health care settings.

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Section: Discussionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Lindsley

King

Thewlis

et al. 2012

Journal of Occupational and Environmental Hygiene

102

View full text Add to dashboard Cite

show abstract

“…To implement appropriate infection control measures and prevent the transmission of contagious diseases from a patient to other people or from outsiders, such as health care personnel and visitors, to the susceptible patient, hospitals must have Airborne Infection Isolation Room (AIIR) which is a safe and healthy environment for patients with infectious diseases [2].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the effect of visitor's movement on bacteria-carrying particles distribution in hospital isolation room

2017

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Abstract. The aim of this paper is to simulate numerically the air ow induced by a walking visitor and its e ects on the contaminant transport and ventilation system e ectiveness. To this end, the following models will be used in this study: the Lagrangian Discrete Random Walk (DRW) model to trace the motion of BCPs, the dynamic mesh method to simulate the visitor movement, and the Reynolds Averaged Navier-Stokes (RANS) model to solve the air ow. The validation results of the numerical method are in full agreement with the available experimental data in the literature. The ndings of the present study indicate that the visitor's movement has remarkable e ect on the basic air ow, and the increase of the visitor moving speed can decrease the risk of infection in the AIIR. It is also found that the concentration of BCPs in the back of visitor exceeds 10 cfu/m 3 , and the small distance between the patient and visitor has a negative impact on increasing the BCPs infection of the patient in AIIR. At the same time, it is observed that the e ect of walking speed on the ventilation e ectiveness index is not remarkable.

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“…Another study in an air cabin by Sze found that the high mass of deposited expiratory aerosols (60%-70% mass of the dye found in air cabin) indicated that the risk from indirect contact transmission is also significant, besides risk from airborne particles. Qian and Li (2010) conducted an experimental and numerical study in a six-bed airborne infection isolation room with downward ventilation (as recommended by Center for Disease Control and Prevention, CDC). Based on the results, they stated that systems with only ceiling-level exhausts can remove gaseous pollutants and fine particles in an isolation room more efficiently than systems with only floor-level exhausts or systems with exhausts at both levels.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of Interpersonal Exposure of Sneezing in a Full-Scale Chamber

Seepana

Lai

2012

Aerosol Science and Technology

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It is well known that person-to-person spreading of infectious pathogens occurs mostly because of sneezing or coughing in indoor environments. This study analyzes the spatial droplet concentration generated by human sneezing and its potential impact on the adjacent person, experimentally and numerically. Experiments were carried out in a controlled chamber with dimensions of 2.3 × 2.3 × 2.3 m 3 with two manikins (source and susceptible) standing opposite to each other at a fixed distance. Two kinds of ventilation schemes were employed in this study: well-mixed ventilation (WMV) and displacement ventilation (DV). For each ventilation scheme, the manikins were placed at two different locations: one at the center and the other near the wall on the right side of the room. Numerical simulations of sneezing droplets distribution in the room were conducted with a drift-flux model to account for the influence of the thermal plume around the human body. The results show good agreement between experimental measurements and computational fluid dynamics (CFD) predictions for vertical temperature profiles in the room and reasonably good agreement between normalized peak aerosol concentrations and the time at which peak concentrations occur. Results for measured points indicated that droplet concentrations around the susceptible manikin were higher when the manikins were placed near the wall, rather than at the center.

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Removal of exhaled particles by ventilation and deposition in a multibed airborne infection isolation room

Cited by 122 publications

References 21 publications

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Numerical simulation of the effect of visitor's movement on bacteria-carrying particles distribution in hospital isolation room

Experimental and Numerical Investigation of Interpersonal Exposure of Sneezing in a Full-Scale Chamber

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