Résumé
Airborne transmission is worldwide popular topic with numerous discussion and researches since influenza pandemic could cost the global economy a lot. In this part of research, we mainly focus on the mechanisms of airborne transmission, together with some determinant factors that influence the spread of aerosols like temperature, humidity and particle size. Finally with several existed cases, insisting masks wearing, especially with three-layer masks wearing are necessary in nowadays for efficiently preventing the transmission of airborne diseases up to 90%. Other possible infection control measures like 2m social distancing are also needed as hygiene measures. © 2023 SPIE.
Résumé
To assess the implications of air conditioning and ventilation on droplet and airborne transmission of SARS-COV-2, several scientific research databases were searched and cross-referenced. Then, an analysis was conducted on the findings pertinent to interaction between several environmental variables affected by HVAC systems and their effect on Virus transmission. The results suggest that airflow velocity may interfere with the trajectories of large respiratory droplets and aerosols. Lower relative humidity provided suitable conditions for virus survival whereas higher temperatures increased aerosol formation, but were detrimental to virus survival. Suboptimal temperatures and humidity can compromise pathogen filtration functions in the nose, while proper use of HVAC functions can help preserve them. Transmission of SARS-COV-2 is not affected solely by the virus's internal properties. Ambient conditions, whether natural or modified by HVAC systems can have a significant effect on the transmissibility and virulence of both the virus and virus-related sickness. The current infection prevention measures, such as social distancing, need to be revised in certain scenarios where natural ventilation or HVAC systems are involved. This will offer, hopefully, higher protection from infections with SARS-COV-2 and similar pathogens. © 2023 by the authors.
Résumé
This investigation presents results of Computational Fluid Dynamics (CFD) modelling of aerosol behaviour within an arbitrary 'realistic' 100m2 office environment, with dynamic and variable respiratory droplet release profile applied based on published findings (Morawska et al., 2009). A multitude of ventilation strategies and configurations have been applied to the base model to compare the effectiveness of reducing the concentration of suspended aerosols over time. A key finding of the investigation indicates a relatively low sensitivity to increasing outside air percentage, and that the benefit from this strategy is heavily dependent on the in-duct droplet decay factor. The application of local recirculating air filtration systems with MERV-13 filters mounted on occupant desks proved significantly more effectiveness than increasing outside air concentration from 25% to 100% in reducing the quantity of suspended aerosols. This highlights that the ventilation industry should perhaps focus on opportunities to integrate filtration systems into furniture, partitions, cabinetry etc., and that an appliance-based solution may be more beneficial for reducing COVID-19 transmission in buildings (and likely more straightforward) than modifications to central ventilation systems, particularly in the application of refurbishments and retrofits. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
A method for determining the presence of SARS-CoV-2 RNA in HEPA filters from portable air cleaners (PACs) have been developed and validated. Herein, a monitoring survey was conducted for 13 weeks in three indoor environments, school, nursery and a household of a socio-sanitary center in Ciudad Real, Spain. In this study, we employed environmental monitoring by RT-PCR of the presence of SARS-CoV-2 in HEPA filters and other surfaces of these indoor spaces for a selective screening in asymptomatic population groups. The aim was to limit outbreaks in an early stage. Only one HEPA filter tested positive in the socio-sanitary center. After analysis by RT-PCR of SARS-CoV-2 in residents and healthcare workers, one worker tested positive. Therefore, this study provides direct evidence of virus-containing aerosols trapped in HEPA filters and the possibility of using these PACs for environmental monitoring of SARS-CoV-2 while they remove airborne aerosols and trap the virus. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
To quantitatively evaluate the effect of increasing ventilation using the immediately practicable method on infection risk, the ventilation rate in a classroom was measured by the concentration decay method using CO2. The measured value was then substituted into the Wells-Riley model to evaluate aerosol infection risk in steady and non-steady states. In the classroom, the air change rate per hour (ACH) ranged from 3.1 to 10.2, and the local mean age of air tended to be larger near the outlet. It was also shown that opening the windows increased the ventilation rate the most, resulting in a more evenly distributed local mean age of air. We also showed that the aerosol infection risk in the classroom could be significantly reduced by increasing ventilation, suppressing vocalization, and wearing a mask, compared to some outbreaks of COVID-19. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
Viral RNA in fine (< 5 µm) aerosols from 13 patients infected by the SARS-CoV-2 virus were obtained using the Gesundheit-II (G-II) equipment which collects respiratory emissions. The collection was performed in isolation wards of the National Centre for Infectious Diseases of Singapore under an approved protocol. The patients breathed normally for 30 minutes, talk, and sing for 15 minutes each (with 30 minutes rest in between activity) into a specially designed aerosol collector in two size fractions. The coarse fraction (> 5 µm) and the fine aerosols (< 5 µm) are subsequently collected and subjected to PCR analysis for their viral load quantification. Viral RNA detected from 59% of the patients showed that patients earlier in illness were more likely to emit detectable RNA, and loads differed significantly between breathing, talking, and singing. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
In the context of the Corona pandemic the investigation of aerosol spreading is utmost important as the virus is transported by the aerosol particles exhaled by an infected person. Thus, a new aerosol generation and detection system is set up and validated. The system consists of an aerosol source generating a particle size distribution mimicking typical human exhalation with particles sizes between 0.3-2.5 µm and an array of Sensirion SPS30 particulate matter sensors. An accuracy assessment of the SPS30 sensors is conducted using a TSI OPS3330, a high-precision optical particle sizer. Low deviations of ±5 % of the particle concentration measured with the SPS30 with respect to the OPS are reported for concentrations below 2'500/cm3 and +10% for particle densities up to 25'000/cm3. As an application example the system is employed in a short distance single-aisle research aircraft Dornier 728 (Do728) located at DLR Göttingen, to investigate the large-scale aerosol-spreading. With this measurement system spreading distance from an index passenger extending one seat row to the front and two seat rows to the back is determined. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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Covid-19 has highlighted the need for reliable methods for airborne microbe control. Different microbes are suitable for different purposes, and the microbes are sensitive to collection methods used. We identified three safe-to-use microbes suitable for airborne microbial studies: MS2-bacteriophage virus, Staphylococcus simulans and Bacillus atrophaeus bacterial spores. We found that the sensitive microbes (MS2 and S. simulans) survive better, when collected directly in a liquid media. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
Adequate and efficient building ventilation and filtration are key factors that play an important part in controlling the spread of airborne pathogens like SARS-CoV2 virus (Allen and Ibrahim, 2021). However, most public buildings lack the ability to test and verify performance of their HVAC and mechanical systems for airborne pathogens due to limitations in existing diagnostic assessment tools. Carleton University performed air sampling campaigns in 24 different spaces to assist in the assessment of our HVAC systems performance across campus. The sampling campaign collected over 600 aerosol samples using veriDART's patented DNA-tagged tracer particles that simulate airborne pathogen mobility and exposure within and between rooms. The primary goal of the survey was to assess aerosol migration at the floor level as well as the potential dilution rate of COVID-19 aerosols. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
The Covid-19 pandemic reminded us the importance of maintaining adequate indoor air quality to reduce the risk of propagation of viral particles. The aim of this study is to use air handling unit (AHU) filters to develop a methodology to identify microbial contaminants present in office indoor air. The methodology involves discs of filter media collected periodically from the extraction filters and analysed by cultural and molecular methods. Results obtained from the 10 months study indicate in particular that the concentration of cultivable microorganisms on the filters display small variations of 37% from average value for the 5-culture media tested (e.g., 3.9×102 CFU/cm2 for LB medium). The genera Aspergillus, Cladosporium and Penicillium are the most represented among the cultivable microorganisms collected on the extraction filter. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
Anthropogenic aerosols mask the climate warming caused by greenhouse gases (GHGs). In the absence of observational constraints, large uncertainties plague the estimates of this masking effect. Here we used the abrupt reduction in anthropogenic emissions observed during the COVID-19 societal slow-down to characterize the aerosol masking effect over South Asia. During this period, the aerosol loading decreased substantially and our observations reveal that the magnitude of this aerosol demasking corresponds to nearly three-fourths of the CO2-induced radiative forcing over South Asia. Concurrent measurements over the northern Indian Ocean unveiled a ~7% increase in the earth's surface-reaching solar radiation (surface brightening). Aerosol-induced atmospheric solar heating decreased by ~0.4 K d−1. Our results reveal that under clear sky conditions, anthropogenic emissions over South Asia lead to nearly 1.4 W m−2 heating at the top of the atmosphere during the period March–May. A complete phase-out of today's fossil fuel combustion to zero-emission renewables would result in rapid aerosol demasking, while the GHGs linger on.
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Uniform practices and quality control methods are needed to detect and quantify airborne viruses across sampling and analysis platforms. We compared detection of airborne SARSCoV-2 RNA in residences of individuals with COVID-19 using two commonly used criteria: environmental (at least one SARS-CoV-2-specific gene and internal control amplified by PCR with Ct ≤ 40) and clinical (at least two SARS-CoV-2-specific genes and internal control amplified with Ct ≤ 37). 24-hr total aerosol samples were collected in a self-isolation room and an additional room without manipulating subjects' behavior/activities. Under the environmental criterion, 7/16 samples in primary rooms and 7/15 samples in secondary rooms were positive. Comparable but lower positive sample proportions were observed using the more rigorous clinical criterion: 6/16 primary rooms and 5/15 secondary rooms. A consensus SARS-CoV-2 environmental sampling and analysis framework is needed for comparisons between studies. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
The theoretical model of the relationship among dose-response function parameters, quantum emission rate, and basic reproductive number for SARS-CoV-2 was constructed. Then, using this model, infection fields and pathways for SARS-CoV-2 and its variant were estimated. The parameters of the time activity, the number of contacts by the microenvironments and groups, and the COVID-19 risk from multiple pathways in near and far fields were used. Consequently, in lower transmissibility, droplet spray transmission in the near field was dominant, whereas in higher transmissibility, transmission from inhalation of smaller aerosols in the far field was dominant. Moreover, it was suggested that transmission from droplet spray, indirect contacts, and inhalation of smaller aerosols in the near field and inhalation of smaller aerosols in the far field was dominant for the wild-type strain, while transmission from inhalation of smaller aerosols in the far field were dominant for the Delta variant. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
This study combines particle measurements and acoustic measurements to study aerosols generated in breathing, speaking, singing and coughing. Particle measurements are carried out using a portable measurement chamber designed specially for the study. Acoustic measurements of voice production are conduced to standardize measurements in human aerosol emission and to reveal possible reasons for the individual differences in particle generation. Understanding mechanisms of human aerosol generation is important in trying to understand how the airborne transmission of pathogens takes place and furthermore in assessing how to minimize the risk of transmission. The results can be used in the context of all airborne diseases. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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On March 11, 2020, the World Health Organization (WHO) designated the new coronavirus COVID-19 to be epidemic. Adherence to infection control methods is strongly affected by an individual's knowledge, attitudes, and practices (KAP). The study aimed to evaluate medical students' understanding, and attitudes toward COVID-19 at the Kirkuk Medical College in Iraq. From October 16 to October 26, 2020, a cross-sectional online study was conducted, among a sample of students in Kirkuk Medical College, one of the Iraqi governorates. A total of 214 students were included in this research, and the age varied between 20-25 years. The questionnaire was divided into demographic data, knowledge, attitudes, and practices, modified from an online questionnaire regarding COVID-19 previously used. Descriptive statistics and t-tests were conducted. Among the study sample (n=214), age ranged between 20-25 years, 72.9% were females, and 86.9% resided in urban areas. The learning questionnaire's total accuracy rate was 96.3%. 98.1% of the students know that the virus is spreading by respiratory droplets from infected individuals, 30.4% have a good attitude towards COVID-19, and 100% have good practice dodging crowded places and practicing appropriate hand hygiene. The majority of students are knowledgeable of disease transference prevention and good practices. Female gender and urban residency play a positive role in knowledge and practice in respect to COVID-19 but not in what concerns the attitude. It is recommended to continue health education programs to correct the negative attitude among students, especially those who reside in rural areas.Copyright © 2023, Codon Publications. All rights reserved.
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In this paper a numerical methodology for close proximity exposure (<2m) is applied to the analysis of aerosol airborne dispersion and SARS-CoV-2 potential infection risk during short journeys in passenger cars. It consists of a three-dimensional transient Eulerian-Lagrangian numerical model coupled with a recently proposed SARS-CoV-2 emission approach, using the open-source software OpenFOAM. The numerical tool, validated by Particle Image Velocimetry (PIV), is applied to the simulation of aerosol droplets emitted by a contagious subject in a car cabin during a 30-minute journey and to the integrated risk assessment for SARS-CoV-2 for the other passengers. The effects of different geometrical and thermo-fluid-dynamic influence parameters are investigated, showing that both the position of the infected subject and the ventilation system design affect the amount of virus inhaled and the highest-risk position inside the passenger compartment. Calculated infection risk, for susceptible passengers in the car, can reach values up to 59%. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
PURPOSE: COVID-19 has posed problems for oculoplastic surgeons. One issue we felt needed to be addressed was the way patients are draped for surgery. Traditionally patients are draped with their full face exposed, and as a result, aerosols generated from both the patient and surgical team put the other party at risk. METHODS: We created a new draping technique which would create a physical barrier. A regional survey was undertaken to compare regional oculoplastic draping practices with our practice locally in light of the COVID-19 pandemic. A patient satisfaction survey was also completed to understand the impact of our change in practice. RESULTS: Our regional survey generated 22 consultant responses. 36% (8) continued with their normal practice with the full face exposed. 18% (4) of the responders had modified a cataract drape and 45% (10) used a bespoke drape with or without a mask. We started using this modified drape in June 2020 and in the patient survey, 100 percent of patients felt the drape was comfortable and 30% of the patients commented on the relief that they did not have to wear a face mask during surgery. CONCLUSIONS: Our draping technique provides an alternative to the traditional full face exposure draping. It is simple, inexpensive, and readily available. It also addresses and resolves the issue of safety of the oculoplastic surgeon and surgical team whilst maintaining comfort for the patient throughout, particularly when risks the of COVID are ongoing and with the potential of more viruses in the future.
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Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2. (SARS-CoV-2). It spreads mainly through saliva droplets or nasal discharge. Dentists are among the professionals with the greatest risk of contracting and transmitting COVID-19. We compared the efficacy of surgical masks versus N95 respirators in preventing COVID-19 infection in dental settings. PubMed, Scopus, Web of Science, and Cochrane Library databases were searched. Search terms corresponded to a predefined PICOS (patient/population, intervention, comparison, and outcomes) question. The risk of bias was evaluated using AMSTAR-2 (A Measurement Tool to Assess Systematic Reviews-2), ROBIS (Risk of Bias in Systematic Reviews), and Health Evidence tools. A total of 191 articles were screened, and nine of them were further evaluated for eligibility, of which five articles (fulfilled the selection criteria) and were included in this study. Two studies concluded that surgical masks could provide equivalent protection to N95 respirators. Another study found that N95 respirators were superior to surgical masks. The fourth study found that better protection can be achieved when using surgical masks by the aerosol source than when the recipient uses an N95 respirator, while the last study concluded that surgical masks or N95 respirators alone do not provide full protection. Thus, according to this systematic review, N95 respirators provide better protection against COVID-19 infection compared to surgical masks.