Résumé
Risk assessment models typically assume ideal mixing, in which the pathogen-laden aerosol particles emitted by a person are evenly distributed in the room. This study points out the local deviation from this idealized assumption and a correlation between the level of pathogen concentration and the distance from the emitter. For this purpose, several numerical studies (CFD) were analyzed, and a validation experiment was performed. Statistical evaluation of the spatial pathogen distribution was used to determine the potential exposure to elevated pathogen concentrations. Compared to an ideally mixed room, at a distance of 1.5 m, the mixing ventilation cases show a 25% risk of being exposed to twice the amount of pathogens and a 5% risk to more than 5 times the assumed value. For displacement ventilation there is a 75% chance of being exposed to less pathogens than in complete mixing at a distance of 1 m. The measurement values agree with the simulation results. © 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
In this study, the nurse's workload in a medical intensive care unit (ICU) was analyzed through the measurement of travel distances and compared between before the pandemic in Feb 2020 and during the pandemic in Feb 2021. The total moving distance of each ICU nurse in four main locations (i.e., a nurse station, central desk, patient room, and hallway) was collected by using the near-field electromagnetic ranging system, which is the advanced real-time location system. We hypothesized that the COVID-19 pandemic significantly influences the nurse's travel distance. The results showed no significant difference in travel distance at the central desk between the Feb and July data. However, the ICU nurse's travel distance in the patient room was significantly increased while the travel distances in the hallway and nurse station were decreased. The findings from this study will help us to understand how the pandemic affects the nurses' workload in a medical intensive care unit. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022.
Résumé
This study presents the transmission of SARS-CoV-2 in the main types of public transport vehicles and stations to comparatively assess the relative theoretical risk of infection of travelers. The presented approach benchmarks different measures to reduce potential exposure in public transport and compares the relative risk between different means of transport and situations encountered. Hence, a profound base for the selection of measures by operators, travelers and staff is provided. Zonal modeling is used as the simulation method to estimate the exposure to passengers in the immediate vicinity as well as farther away from the infected person. The level of exposure to passengers depends on parameters such as the duration of stay and travel profile, as well as the ventilation situation and the wearing of different types of masks. The effectiveness of technical and behavioral measures to minimize the infection risk is comparatively evaluated. Putting on FFP2 (N95) masks and refraining from loud speech decreases the inhaled viral load by over 99%. The results show that technical measures, such as filtering the recirculated air, primarily benefit passengers who are a few rows away from the infected person by reducing exposure 84–91%, whereas near-field exposure is only reduced by 30–69%. An exception is exposure in streetcars, which in the near-field is 17% higher due to the reduced air volume caused by the filter. Thus, it can be confirmed that the prevailing measures in public transport protect passengers from a high theoretical infection risk. At stations, the high airflows and the large air volume result in very low exposures (negligible compared to the remaining means of transport) provided that distance between travelers is kept. The comparison of typical means of transport indicates that the inhaled quanta dose depends primarily on the duration of stay in the vehicles and only secondarily on the ventilation of the vehicles. Due to the zonal modeling approach, it can also be shown that the position of infected person relative to the other passengers is decisive in assessing the risk of infection. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Résumé
We demonstrate the THz near-field nano-imaging of Bacillus cereus and Corona Virus Disease 2019 (COVID-19) spike fake virus utilizing THz scattering near-field optical microscopy (SNOM). Here, it shows that bacteria and virus can be distinguished from other substances by THz near-field imaging. And we can use the THz time-domain spectrometer (TDS) scattering near field microscope(s-SNOM) to obtain the spectrum of different substances (bacteria and their substrate), then analyzing the differences between them from their specific responses in THz. This is of great significance to development of the terahertz near-field biology. © 2021 European Union