Sufficient Ventilation Research Articles

An Analysis of Urban Vehicle Body Aerodynamics Using Computational Fluid Dynamics for the Shell Eco-Marathon Challenge

The Shell Eco-Marathon challenge is an annual competition held to challenge students in innovating the most fuel efficiency vehicle for either a prototype or an urban concept vehicle. An urban concept vehicle is designed for fuel efficiency using electricity as source of power. Apart from the use of electricity as an alternative to internal combustion engines, the design of the vehicle is also crucial for efficiency. The car bodywork design needs to be aerodynamically designed to minimise drag and subsequently use less energy to move. The design must also incorporate structural integrity to protect the driver as well as providing airflow for sufficient ventilation both inside the passenger and the engine compartment. Five models for the rear and front designs were produced using CATIA and analysed using Computational Fluid Dynamics in ANSYS Fluent. The models underwent a virtual wind tunnel on three different air velocity speeds, 20 km/h, 30 km/h and 40 km/h to generate a force report of drag force and coefficient on each design. The front design is chosen based on the lowest drag coefficient and force while the rear design is selected based on a balanced downforce while achieving the lowest practical drag force. The results demonstrated that the air resistance faced by a car was highly influenced by both front and rear design of the body.

Assessing the “sufficient ventilation” requirement for Austrian buildings: development of a Monte Carlo based spreadsheet calculation to estimate airing intervals and mould risk in window ventilated buildings

In Austria the lack of guidelines or standards has caused many discussions and disputes on the question if “sufficient ventilation” can be ensured with window airing only, in particular in newly constructed, airtight residential buildings. This work presents the development of a calculation method aiming to provide a simple-to-use tool to estimate the risk of mould growth and the window airing interval required to ensure good indoor air quality assuming a range of different boundary conditions and occupant behaviours. The method implements a Monte Carlo approach calculating 1000 single zone mass balances for carbon dioxide (on a room level) and water vapor (on a housing level). Air infiltration through the building envelope is accounted using the so-called LBL-model. The time interval between window airing required to comply with CO2 limit value is estimated by calculating the time evolution of the CO2 concentration for 1000 different parameter combinations. The mould risk is estimated by a 1000-fold calculation of the daily averaged indoor air humidity and the resulting water activity on critical wall surfaces. The results are displayed as probability distributions providing information on the risk that the queried situation can or cannot ensure “sufficient ventilation”. Exemplary calculations for bedrooms of new multifamily buildings estimate that intervals between window airing events (to keep time-averaged CO2-concentration below 1000 ppm), will vary between 23 and 190 minutes (representing the 5th and the 95th percentile). This is clearly below an acceptable intervention interval for bedrooms. For living rooms, the assessment shows a strong sensitivity on the “accessible” air volume. The humidity assessment for this type of housing suggests that mould growth could occur in about 17% of the cases even though air exchange corresponding to two airing events per day were assumed. An additional outdoor air exchange of up to 40 m³/h would be required to reduce the mould risk fraction to <1%, suggesting the need for mechanical ventilation concepts in residential housing to enable healthy indoor environment independently of occupant behaviour.

Characteristics and Outcomes of Emergency Transferred Patients with Foreign Body Airway Obstruction in Tokyo, Japan.

Foreign body airway obstruction (FBAO) is a life-threatening emergency, and the prognosis of patients with FBAO is greatly affected by the prehospital process. There are only a few large-scale studies analyzing prehospital process databases of the fire department. The aim of this study was to investigate whether characteristics of patients with FBAO were associated with prehospital factors and outcomes. In this retrospective observational study, patients transferred to the hospital by the Tokyo, Japan Fire Department for FBAO from 2017 through 2019 were included. The association between neurologically favorable survival among the characteristics of patients with FBAO and prehospital factors affecting the outcomes was evaluated. Of the 2,429,175 patients, 3,807 (0.2%) patients had FBAO. The highest number of FBAO cases was 99 (2.6%), which occurred on January 1 (New Year's Day), followed by 40 cases (1.1%) on January 2, and 28 cases (0.7%) on January 3. The number of patients who experienced out-of-hospital cardiac arrest (OHCA) caused by FBAO was 1,644 (43.2%). Comparing the OHCA and non-OHCA groups, there were significant differences in age, sex, time spent at the site, and distance between the site and hospital. Cardiac arrest was significantly lower in infants after FBAO (P < .001). In total, 98.2% of patients who did not have return of spontaneous circulation (ROSC) before hospital arrival died within 30 days, a significantly higher mortality rate than that in patients who had ROSC (98.2% versus 65.8%; P < .001). Among patients who did not have ROSC following FBAO upon arrival at the hospital, 98.2% died within 30 days. Thus, it is important to remove foreign bodies promptly and provide sufficient ventilation to the patient at the scene to increase the potential for ROSC. Further, more precautions should be exercised to prevent FBAO at the beginning of the year.

Prevalence of COVID-19 in flood relief centre

&lt;p&gt;Since the beginning of 2020, people all around the world have been struggling with the impacts of the COVID-19 pandemic. Concurrently, major flooding and a pandemic have struck numerous regions of the world. As a result, relief centres for flood victims have been established in the affected regions. There is a risk of COVID-19 infection spreading among flood victims and workers at flood relief centres due to the enormous number of flood victims. This study focused on the Johor, Malaysia flood catastrophe. From the 1st to the 16th of January 2022, a cross-sectional study was conducted in johor flood relief centres using secondary data from E notification and COVID-19-line listing. 1,531 flood victims were examined for COVID-19 and Rapid antigen testing was performed. 711 victims were asymptomatic, whereas 820 victims were symptomatic. Six patients were identified as positive. During audits of multiple evacuation centres, few concerns were found. There was no sufficient ventilation, there was no distribution of face masks to victims, and there were no daily health checks. COVID-19 preventive measures in all evacuation centres need to be practiced and given attention by all occupants and agencies.&lt;/p&gt;

Can positive input ventilation tackle surface condensation and mould growth? Literature review and case study of a UK dwelling

Insufficient ventilation is one of the main factors leading to damp and mould in residential buildings. One low-cost method to improve these moisture-related issues is positive input ventilation (PIV) but research data on performance is scarce in the literature. This paper presents a bibliographical review together with a case study based on monitoring a residential building by means of environmental sensors. The review reveals the importance of correct location, installation, operation and continued maintenance of mechanical ventilation systems. Specifically, PIV and exhaust ventilation units in existing buildings require routine checking to ensure these systems are working correctly and efficiently. The results of monitoring ambient and surface temperature and relative humidity show that the PIV and enhancement extract fan set-up can reduce atmospheric moisture levels and avoid surface condensation. Mould growth is no longer active, but it is always essential to perform thoughtful building inspections checking the right conditions for installation and maintenance to ensure the proper functioning of the units. It is critical to study the size of the building and structural characteristics of the roof and ceilings. Also to verify that the doors are well undercut to allow air flow and that the occupancy levels and regional climate are adequate for selecting the appropriate type of mechanical ventilation units and corresponding operational modes (flow rates, operational settings, etc.). More research, measurements and monitoring studies pre- and post-installation of PIV and other whole house mechanical ventilation systems are recommended to assess optimal performances. This could also help to ensure the success of retrofitting projects in residential buildings which aim to improve energy efficiency but also make buildings relatively airtight and prone to condensation damp. An effective, sufficient and appropriate ventilation system as well as a good installation practice and adequate maintenance is key to avoid surface condensation and mould growth and to improve the indoor air quality of both new and existing buildings.

A Detailed Study of the Radon and Progeny Levels in Houses of Bangalore Metropolis, Karnataka, India

Introduction: Radon, a radioactive inert gas that makes up a significant portion of the background radiation to which people are exposed, can endanger public health when it builds up in inadequately ventilated residential and commercial spaces. The lungs' exposure to alpha particles after inhaling Radon decay products accounts for around half of the overall radiation effective dose to the general public. Objectives: To observe the variation of radon and progeny levels in different locations and different houses of Bangalore city having variety of features viz., season, walls, rooms, flooring, volume and diurnal various. Methods: Standard protocols provided by Environmental Assessment division, Bhabha atomic research centre, Mumbai is followed for the all the measurements. Results: In this outlook, the interior atmosphere must have to be carried out for both 222Rn (radon) and 220Rn (thoron) levels in order to provide an accurate assessment of the natural breathing dose. For the present study a sizable number of measurements had been made for more than eight years which examined the effective dose rates caused by indoor levels of 222Rn, 220Rn, and their progeny during various seasons of the year. In order to lessen the effective dosage rate, it is advised that lower size houses have sufficient ventilation and granite floorings to be avoided. Conclusions: More thorough research should be planned and carried out in this area and across the nation on the evaluation of public exposure to natural radiation, particularly the exposure from 222Rn, 220Rn and their offspring.

РАЗРАБОТКА И ВАЛИДАЦИЯ СПЕКТРОФОТОМЕТРИЧЕСКОЙ МЕТОДИКИ ОПРЕДЕЛЕНИЯ СОДЕРЖАНИЯ ФЛАВОНОИДОВ В ПУПАВКИ КРАСИЛЬНОЙ ТРАВЕ

The aim of this work is development and validation of a spectrophotometric technique for quantification of total flavonoids in terms of rutin in potentially medicinal plant Anthemis tinctoria herb. According to the literature, Anthemis tinctoria is used in folk medicine as a hepatoprotective, hemostatic and means, and its extracts in the experiment exhibit antimicrobial, cytostatic and antioxidant activities. In this work, we used sample of Anthemis tinctoria herb harvested in the summer of 2021 during the period of mass flowering in vicinity of Perm city (valley of the Vasilievka river, Adishchevo railway station). The raw materials were dried at room temperature, with sufficient ventilation, without direct exposure to sunlight, stored separately from other types of raw materials. According to the experiments the optimal conditions for determining of total flavonoids: grinding the raw material to a size passing through a sieve with a diameter of 1 mm, the optimal concentration of ethyl alcohol extractant is 50%, the analytical wavelength is 410 nm, the extraction time in a boiling water bath is 45 minutes, the ratio of extraction and complexing agent - 2% alcohol solution of aluminum chloride - 2:5. The technique was validated in accordance with the requirements of State Pharmacopeia of Russia 14th edition, the relative error of determination with a reliable probability of 95% was 4.00%. The technique can be used in further work to conduct studies of biological activity.

Characterizing the induced flow through the cavity of a wall solar chimney under the effects of the opening heights

Using solar chimneys in buildings can enhance the thermal insulation of the building envelope and provide sufficient ventilation and cooling. The performance of a solar chimney is strongly affected by its configurational factors. This work examines the effects of the opening heights on the flow field in the cavity of a wall solar chimney with a Computational Fluid Dynamics (CFD) model. Both cases of equal and unequal opening areas were considered. The results show that the induced flow rate increases with the opening height and gradually becomes constant as the opening height is about 2.0–3.0 and 5.0–6.0 times the air gap for heating the left wall (HLW) and the right wall (HRW) of the air cavity, respectively. Particularly, using equal inlet and outlet heights that are equal to the air gap reduces the flow rate of 27% for HLW and 85% for HRW compared to the maximum ones. The optimal design of a wall solar chimney to achieve maximum flow rate is proposed for two cases of heating, that is, (a) for HLW, equal opening heights which are twice the air gap, and (b) for RHW, the inlet height equal to the air gap, and the outlet height equal to five times the air gap.

Active Air Monitoring for Understanding the Ventilation and Infection Risks of SARS-CoV-2 Transmission in Public Indoor Spaces

Indoor, airborne, transmission of SARS-CoV-2 is a key infection route. We monitored fourteen different indoor spaces in order to assess the risk of SARS-CoV-2 transmission. PM2.5 and CO2 concentrations were simultaneously monitored in order to understand aerosol exposure and ventilation conditions. Average PM2.5 concentrations were highest in the underground station (261 ± 62.8 μgm−3), followed by outpatient and emergency rooms in hospitals located near major arterial roads (38.6 ± 20.4 μgm−3), the respiratory wards, medical day units and intensive care units recorded concentrations in the range of 5.9 to 1.1 μgm−3. Mean CO2 levels across all sites did not exceed 1000 ppm, the respiratory ward (788 ± 61 ppm) and the pub (bar) (744 ± 136 ppm) due to high occupancy. The estimated air change rates implied that there is sufficient ventilation in these spaces to manage increased levels of occupancy. The infection probability in the medical day unit of hospital 3, was 1.6-times and 2.2-times higher than the emergency and outpatient waiting rooms in hospitals 4 and 5, respectively. The temperature and relative humidity recorded at most sites was below 27 °C, and 40% and, in sites with high footfall and limited air exchange, such as the hospital medical day unit, indicate a high risk of airborne SARS-CoV-2 transmission.

Energy-efficient virtual sensor-based deep reinforcement learning control of indoor CO2 in a kindergarten

High concentrations of indoor CO2 pose severe health risks to building occupants. Often, mechanical equipment is used to provide sufficient ventilation as a remedy to high indoor CO2 concentrations. However, such equipment consumes large amounts of energy, substantially increasing building energy consumption. In the end, the issue becomes an optimization problem that revolves around maintaining CO2 levels below a certain threshold while utilizing the minimum amount of energy possible. To that end, we propose an intelligent approach that consists of a supervised learning-based virtual sensor that interacts with a deep reinforcement learning (DRL)-based control to efficiently control indoor CO2 while utilizing the minimum amount of energy possible. The data used to train and test the DRL agent is based on a 3-month field experiment conducted at a kindergarten equipped with a heat recovery ventilator. The results show that, unlike the manual control initially employed at the kindergarten, the DRL agent could always maintain the CO2 concentrations below sufficient levels. Furthermore, a 58% reduction in the energy consumption of the ventilator under the DRL control compared to the manual control was estimated. The demonstrated approach illustrates the potential leveraging of Internet of Things and machine learning algorithms to create comfortable and healthy indoor environments with minimal energy requirements.

Airway management with novel intubating laryngeal tubes has no influence on cerebral oxygenation in cardiac surgery patients: A prospective observational study

BackgroundA laryngeal tube is often used as an alternative to intubation with direct laryngoscopy during cardiopulmonary resuscitation. However, in a study with piglets undergoing simulated cardiac arrest, reduced carotid artery blood flow was associated with the insertion of different supraglottic airway devices, such as a laryngeal tube. Limited by its construction, secondary tracheal intubation through a laryngeal tube was difficult or impossible in contrast to a second generation laryngeal mask. The new disposable intubating laryngeal tube with suction (iLTS-D®) seems to facilitate tracheal intubation. We hypothesized that iLTS-D, when inflated to the recommended air volume, does not reduce cerebral oxygenation in patients with cardiovascular diseases undergoing elective cardiac surgery.MethodsThis single-center prospective, controlled observational study was approved by the local ethics committee (Ethical Committee No. 2018-13716). Forty adult patients undergoing elective cardiac surgery requiring tracheal intubation were included in this study. The exclusion criteria were age &amp;lt;18 years and a high risk of aspiration, inability to consent, height &amp;lt;155 cm, or pregnancy. Prior to insufflation and deflation of the cuffs, we performed cerebral oximetry via near-infrared spectroscopy. The primary outcome was a significant reduction in NIRS in the context of the preinduction baseline value after inflation of the cuffs with the recommended air volume, defined as a ≥25% decrease from baseline or an absolute value ≤ 50%. The secondary endpoints were differences in time points, insertion success rates, and complications.ResultsThere was no significant reduction in cerebral oximetry after inflation with the recommended cuff volume and an initially measured cuff pressure of &amp;gt;120 cmH2O. Overall, tracheal intubation was achieved in a median of 20 s [interquartile range 15-23 s] and enabled sufficient ventilation and tracheal intubation through the iLTS-D in all patients. Traces of blood on the cuffs (after removing the iLTS-D) and a sore throat (evaluated 2 h after removing the tracheal tube) were observed in one patient.ConclusionOur results showed no association between the insertion of the iLTS-D and reduced cerebral oxygenation in patients undergoing elective cardiac surgery.Trial registrationClinicalTrials.gov, NCT03942809.

The changing role of BIM-facilitated facilities management in the post-COVID era: A systematic literature review

COVID-19 has become a long-term pandemic and pushed the re-interpretation of normality. Fighting against the pandemic and building a new normal in the post-COVID era requires constant and innovative approaches. Building information modeling (BIM) facilitated facilities management (FM) has been advocated as a powerful method to overcome the huge public health-related challenges. However, studies investigating the role of BIM-facilitated FM in the pandemic era are fragmented, and holistic knowledge is limited. Research objectives of this study are twofold: (1) to identify varying FM requirements after the outbreak of COVID-19, (2) to investigate how BIM-facilitated FM copes with changing requests in the pandemic period. To achieve the objectives, a systematic literature review was conducted. Currently, FM tends to be public health-centric, and highly emphasized requirements encompass the flexibility of space transformation for emergency purpose, effective and sufficient ventilation, reliable biosecurity, and strict anti-infection management. Based on centralized database and visualized model, BIM-facilitated FM enables space optimization, simulation and prediction of infection risk, monitoring and managing equipment operation, and effective information management, which enhances both hard and soft FM. This paper sheds light on the applications and directions of future BIM-facilitated FM research in protecting public health in the post-COVID era.

Yoğun Bakım Ünitelerinde Çalışan Hemşirelerin Kaf Basıncı Eğitim Yeterliliği

Aim: The convenient cuff pressure of the endotracheal tube, fixes the tube in the correct position , provides sufficient ventilation, and prevents complications. In this study, we aimed to evaluate the adequacy of the training and experience of nurses working in the intensive care units on cuff care in patients with intubation and tracheostomy. Material and Methods: Fifty nurses working in intensive care units in chest diseases hospital agreed to participate in the study. The 10-question questionnaire was asked face-to-face to the participating nurses and their answers were recorded. Results: Twenty three nurses (46%) surveyed had more than 5 years of intensive care experience. Thirty five nurses (70%) had bachelor's degree. To the question of ‘what is the cuff function?’, 72% of the nurses who participated in the survey answered as fixing the tube, 64% as preventing air leakage, and 44% as protecting the lungs from gastric secretions. According to intensive care unit working time, the rate of training on cuff pressure is statistically significantly higher in people who have worked for 5 years or more than those who have worked for less than 5 years. In terms of all questions, there is no statistically significant difference according to education level. Conclusion: The nurses working in our intensive care unit had lack of knowledge and lack of training about cuff pressure monitoring and cuff exercises. Nurses working in intensive care units should be given in-service training on cuff pressure and cuff exercises.

A Case of Metastatic Tumor Totally Obstructing Lower Trachea Removed by Ventilating Bronchoscopy and Suspension Laryngoscope With Extracorporeal Membrane Oxygenation

A patient diagnosed with advanced lung cancer developed severe dyspnea after chemotherapy. Metastatic tumor completely obstructing the lower trachea was revealed by bronchoscopy. Emergent surgery was required but it was difficult to perform open tracheal surgery and maintain sufficient ventilation with tracheal intubation because of location and size of the tumor. After consultation with an esthesiologist, respiratory physician and cardiothoracic surgeon, we performed surgery with extracorporeal membrane oxygenation (ECMO) without intubation. We report a rare case of a successfully removed metastatic tumor in the airway under the support of ECMO.

A post-occupancy study of ventilation effectiveness from high-resolution CO2 monitoring at live theatre events to mitigate airborne transmission of SARS-CoV-2

Mass-gathering events were closed around the world in 2020 to minimise the spread of the SARS-CoV-2 virus. Emerging research on the transmission of SARS-CoV-2 emphasised the importance of sufficient ventilation. This paper presents the results of an indoor air quality (IAQ) monitoring study over 82 events in seven mechanically ventilated auditoria to support the UK government Events Research Programme. Indoor carbon dioxide concentration was measured at high resolution before, during, and after occupancy to allow for assessment of the ventilation systems. Generally, good indoor air quality was measured in all auditoria, with average IAQ found to be excellent or very good for 70% of spaces. In some auditoria, spatial variation in IAQ was identified, indicating poor mixing of the air. In addition, surface and air samples were taken and analysed for the presence of bacteria by culture and SARS-CoV-2 using RT-qPCR in one venue. SARS-CoV-2 RNA was detected on a small number of surfaces at very low copy numbers, which are unlikely to pose an infection risk. Under the ventilation strategies and occupancy levels investigated, it is likely that most theatres pose a low risk of long-range transmission of COVID-19.

Impact of mechanical ventilation control strategies based on non-steady-state and steady-state Wells-Riley models on airborne transmission and building energy consumption.

Ventilation is an effective solution for improving indoor air quality and reducing airborne transmission. Buildings need sufficient ventilation to maintain a low infection risk but also need to avoid an excessive ventilation rate, which may lead to high energy consumption. The Wells-Riley (WR) model is widely used to predict infection risk and control the ventilation rate. However, few studies compared the non-steady-state (NSS) and steady-state (SS) WR models that are used for ventilation control. To fill in this research gap, this study investigates the effects of the mechanical ventilation control strategies based on NSS/SS WR models on the required ventilation rates to prevent airborne transmission and related energy consumption. The modified NSS/SS WR models were proposed by considering many parameters that were ignored before, such as the initial quantum concentration. Based on the NSS/SS WR models, two new ventilation control strategies were proposed. A real building in Canada is used as the case study. The results indicate that under a high initial quantum concentration (e.g., 0.3 q/m3) and no protective measures, SS WR control underestimates the required ventilation rate. The ventilation energy consumption of NSS control is up to 2.5 times as high as that of the SS control.

Indoor air CO2 concentrations and ventilation rates in two residences in İzmir, Turkey

Houses are the places where people spend most of their time. That is why indoor air quality at home is essential for public health. Sufficient ventilation is the factor to avoid accumulation of pollutants in indoor air, which include microorganisms, such as SARS-CoV-2. Therefore, adequate ventilation is needed to provide good indoor air quality for human health and reduce infection risk at home. There are no reports of residential ventilation rates in Turkey. In this study, CO2 concentrations were measured in two residences in Izmir, Turkey. Three experiments were conducted to determine background concentrations and the rate of natural ventilation with infiltration and opening windows. Results show that air exchange provided by infiltration is low for both case rooms, while adequate ventilation could be achieved with natural ventilation under the studied conditions. Infiltration provided air exchange and ventilation rates of 0.18 h-1 and 5.9 m3/h for Case 1 and 0.29 h-1 and 8.23 m3/h for Case 2, respectively. Air exchange and ventilation rates were increased to 2.36 h-1 and 76.9 m3/h for Case 1 and 1.2 h-1 and 34 m3/h for Case 2, respectively, by opening the windows. Although ventilation can be provided by opening the windows, the other factors that determine its rate, e.g., meteorological variables, cannot be controlled by the occupants. Consequently, people cannot ensure the good indoor air quality in bedrooms and sufficient reduction in transmission of pathogenic microorganisms; therefore, risk of spreading diseases such as COVID-19 at home.

Smart control of HVAC based on measurements of indoor radon concentration

Sufficient ventilation is important for creating a healthy indoor environment in both households and larger buildings (schools, offices, shops, warehouses). As the cost of heating and ventilation in large buildings is very large, modern ventilation systems apply smart control for optimizing the energy consumption. The control is typically based on temperature and/or CO2 levels, whereas other pollutants such as particulate microparticles and radon are not accounted for. Exposure to indoor radon is the second most important reason for lung cancer, with more than 200 000 casesestimated worldwide every year. The indoor radon concentration depends on many factors, from local geological conditions and weather, to building materials and natural and mechanical ventilation. Together with the Norwegian company OBEO AS, NORCE has completed a study of the indoor radon concentration at a Norwegian primary school prone to high radon levels. The study includes continuous measurements of radon, CO2 and temperature for multiple rooms for different use as well as data for the ventilation system. The aim for the project was to build knowledge for a larger research project, where the goal is to develop a control algorithm for HVAC systems which also takes radon levels into account. An important challenge is to make accurate sensors for measuring radon continuously at an affordable price for implementation in complex buildings. Generally, sensors that can measure at high frequency with good accuracy is very expensive. Thus, developing algorithms and mathematical models to treat the data from low-cost sensors can be an adequate tool for large systems/buildings. One must also account for the positioning of the sensor. For instance, it is known that the radon concentration is better distributed in a room with mechanical ventilation than in a room without, making the position of the sensor important for better interpretation of measurement data. In the pre-project we have studied how the radon levels show large variations that are related to the ventilation operation and daily/weekly variations. The large variations show the need for a high sampling rate (minutes to hours) to capture the peaks in the concentration. We have also studied the rate of change in radon concentrations over time and have amongst discovered a noticeable delay from the start of ventilation until radon is effectively removed from the air. The rate of change is an important parameter for planning ahead and securing fresh air during the full period of presence whilst optimizing the energy cost.

Probable cross-corridor transmission of SARS-CoV-2 due to cross airflows and its control

A COVID-19 outbreak occurred in May 2020 in a public housing building in Hong Kong – Luk Chuen House, located in Lek Yuen Estate. The horizontal cluster linked to the index case’ flat (flat 812) remains to be explained. Computational fluid dynamics simulations were conducted to obtain the wind-pressure coefficients of each external opening on the eighth floor of the building. The data were then used in a multi-zone airflow model to estimate the airflow rate and aerosol concentration in the flats and corridors on that floor. Apart from flat 812 and corridors, the virus-laden aerosol concentrations in flats 811, 813, 815, 817 and 819 (opposite to flat 812, across the corridor) were the highest on the eighth floor. When the doors of flats 813 and 817 were opened by 20%, the hourly-averaged aerosol concentrations in these two flats were at least four times as high as those in flats 811, 815 and 819 during the index case's home hours or the suspected exposure period of secondary cases. Thus, the flats across the corridor that were immediately downstream from flat 812 were at the highest exposure risk under a prevailing easterly wind, especially when their doors or windows that connected to the corridor were open. Given that the floorplan and dimension of Luk Chuen House are similar to those of many hotels, our findings provide a probable explanation for COVID-19 outbreaks in quarantine hotels. Positive pressure and sufficient ventilation in the corridor would help to minimise such cross-corridor infections.

Particulate matter emissions during autopsies: a method to reduce exposure

Particulate matter emitted during autopsies can serve as a vector for numerous viruses or bacteria and can lead to infections. Reducing the exposure of those particles in indoor working environments is, therefore, an important issue. To assess the health risk for employees in forensic medicine, we measure particulate matter in the ambient air during autopsies by using an aerosol spectrometer. The autopsies were performed with either an ordinary oscillating saw or an adapted saw with a suction unit. The particle emissions from both saws were compared to each other in order to evaluate whether a technical adaption leads to a particle reduction. Furthermore, the particle exposure reduction by wearing a face mask and variations in the background concentration in the room were analyzed. High particle concentrations were measured while using the ordinary saw. By using the adapted saw or wearing a face mask, the particle exposure could mostly be avoided. On the majority of the working days, an increase in the background concentration could be observed. Based on this knowledge, the use of a proper suction unit and wearing a face mask during autopsies is necessary. Besides, it is important to have sufficient ventilation in the room so that long-lasting high background concentrations can be prevented.Graphical abstract