Airflow patterns through single hinged and sliding doors in hospital isolation rooms - Effect of ventilation, flow differential and passage

Heating, ventilation, and air-conditioning systems in healthcare: a scoping review

Guidelines for heating, ventilation, and air-conditioning systems have been developed for different settings. However, there is a lack of up-to-date evidence providing concrete recommendations for the heating, ventilation, and air-conditioning systems of an isolation room, which is essential to appropriately guide infection control policies. To highlight the guidelines for heating, ventilation, and air-conditioning systems in isolation rooms to inform relevant stakeholders and policymakers. A systematic search was performed based on Joanna Briggs Methodology using five databases (CINAHL, Embase, Joanna Briggs Institute, Medline, and Web of Science) and websites. Eight articles published by government departments were included in this review. Most studies recommended controlled airflow without recirculation, 12 air changes per hour, high-efficiency particulate air filtrate to exhaust contaminated air from the airborne isolation room, humidity ≤60%, and temperature in the range of 18-30 °C. This review provides further evidence that there is a need for interdisciplinary collaborative research to quantify the optimum range for heating, ventilation, and air conditioning system parameters, considering door types, anterooms, and bed management, to effectively reduce the transmission of infection in isolation rooms.

A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches

In the past few years, significant efforts have been made to investigate the transmission of COVID-19. This paper provides a review of the COVID-19 airborne transmission modeling and mitigation strategies. The simulation models here are classified into airborne transmission infectious risk models and numerical approaches for spatiotemporal airborne transmissions. Mathematical descriptions and assumptions on which these models have been based are discussed. Input data used in previous simulation studies to assess the dispersion of COVID-19 are extracted and reported. Moreover, measurements performed to study the COVID-19 airborne transmission within indoor environments are introduced to support validations for anticipated future modeling studies. Transmission mitigation strategies recommended in recent studies have been classified to include modifying occupancy and ventilation operations, using filters and air purifiers, installing ultraviolet (UV) air disinfection systems, and personal protection compliance, such as wearing masks and social distancing. The application of mitigation strategies to various building types, such as educational, office, public, residential, and hospital, is reviewed. Recommendations for future works are also discussed based on the current apparent knowledge gaps covering both modeling and mitigation approaches. Our findings show that different transmission mitigation measures were recommended for various indoor environments; however, there is no conclusive work reporting their combined effects on the level of mitigation that may be achieved. Moreover, further studies should be conducted to understand better the balance between approaches to mitigating the viral transmissions in buildings and building energy consumption.

Hospital indoor air quality and its relationships with building design, building operation, and occupant-related factors: A mini-review

Indoor air quality (IAQ) has recently gained substantial traction as the airborne transmission of infectious respiratory disease becomes an increasing public health concern. Hospital indoor environments are complex ecosystems and strategies to improve hospital IAQ require greater appreciation of its potentially modifiable determinants, evidence of which are currently limited. This mini-review updates and integrates findings of previous literature to outline the current scientific evidence on the relationship between hospital IAQ and building design, building operation, and occupant-related factors. Emerging evidence has linked aspects of building design (dimensional, ventilation, and building envelope designs, construction and finishing materials, furnishing), building operation (ventilation operation and maintenance, hygiene maintenance, access control for hospital users), and occupants' characteristics (occupant activities, medical activities, adaptive behavior) to hospital IAQ. Despite the growing pool of IAQ literature, some important areas within hospitals (outpatient departments) and several key IAQ elements (dimensional aspects, room configurations, building materials, ventilation practices, adaptive behavior) remain understudied. Ventilation for hospitals continues to be challenging, as elevated levels of carbon monoxide, bioaerosols, and chemical compounds persist in indoor air despite having mechanical ventilation systems in place. To curb this public health issue, policy makers should champion implementing hospital IAQ surveillance system for all areas of the hospital building, applying interdisciplinary knowledge during the hospital design, construction and operation phase, and training of hospital staff with regards to operation, maintenance, and building control manipulation. Multipronged strategies targeting these important determinants are believed to be a viable strategy for the future control and improvement of hospital IAQ.

Current and potential approaches on assessing airflow and particle dispersion in healthcare facilities: a systematic review

An indoor environment in a hospital building requires a high indoor air quality (IAQ) to overcome patients' risks of getting wound infections without interrupting the recovery process. However, several problems arose in obtaining a satisfactory IAQ, such as poor ventilation design strategies, insufficient air exchange, improper medical equipment placement and high door opening frequency. This paper presents an overview of various methods used for assessing the IAQ in hospital facilities, especially in an operating room, isolation room, anteroom, postoperative room, inpatient room and dentistry room. This review shows that both experimental and numerical methods demonstrated their advantages in the IAQ assessment. It was revealed that both airflow and particle tracking models could result in different particle dispersion predictions. The model selection should depend on the compatibility of the simulated result with the experimental measurement data. The primary and secondary forces affecting the characteristics of particle dispersion were also discussed in detail. The main contributing forces to the trajectory characteristics of a particle could be attributed to the gravitational force and drag force regardless of particle size. Meanwhile, the additional forces could be considered when there involves temperature gradient, intense light source, submicron particle, etc. The particle size concerned in a healthcare facility should be less than 20 μm as this particle size range showed a closer relationship with the virus load and a higher tendency to remain airborne. Also, further research opportunities that reflect a more realistic approach and improvement in the current assessment approach were proposed.

Droplet aerosols transportation and deposition for three respiratory behaviors in a typical negative pressure isolation ward

Negative pressure isolation wards could provide safety for health care workers (HCWs) and patients infected with SARS-CoV-2. However, respiratory behavior releases aerosols containing pathogens, resulting in a potential risk of infection for HCWs. In this study, the spatiotemporal distribution of droplet aerosols in a typical negative pressure isolation ward was investigated using a full-scale experiment. In this experiment, artificial saliva was used to simulate the breathing behavior, which can reflect the effect of evaporation on droplet aerosols. Moreover, numerical simulations were used to compare the transport of droplet aerosols released by the three respiratory behaviors (breathing, speaking, and coughing). The results showed that droplet aerosols generated by coughing and speaking can be removed and deposited more quickly. Because reduction in the suspension proportion per unit time was much higher than that in the case of breathing. Under the air supply inlets, there was significant aerosol deposition on the floor, while the breathing area possessed higher aerosol concentrations. The risk of aerosol resuspension and potential infection increased significantly when HCWs moved frequently to these areas. Finally, more than 20% of the droplet aerosols escaped from the ward when the number of suspended aerosols in the aerosol space was 1%.

The Effectiveness of the Anteroom (Vestibule) Area on Hospital Infection Control and Health Staff Safety: A Systematic Review

The emergence of SARS-CoV2 in 2019 showed again that the world's healthcare system is not fully equipped and well-designed for preventing the transmission of nosocomial respiratory infections. One of the great tools for preventing the spread of infectious organisms in hospitals is the anteroom. Several articles have investigated the role of the anteroom in disease control but the lack of a comprehensive study in this field prompted us to provide more in-depth information to fill this gap. Also, this study aimed to assess the necessity to construct an anteroom area for hospital staff members at the entrance of each ward of the hospital, and specify the equipment and facilities which make the anteroom more efficient. Articles were identified through searches of Scopus, Web of Sciences, PubMed, and Embase for studies published in English until May 2020 reporting data on the effect of the anteroom (vestibule) area in controlling hospital infections. Data from eligible articles were extracted and presented according to PRISMA's evidence-based data evaluation search strategy. Also, details around the review aims and methods were registered with the PROSPERO. From the database, 209 articles were identified, of which 25 studies met the study criteria. Most studies demonstrated that an anteroom significantly enhances practical system efficiency. The results showed that the equipment such as ventilation system, high-efficiency particulate absorption filter, hand dispensers, alcohol-based disinfection, sink, mirror, transparent panel, UVC disinfection, and zone for PPE change, and parameters like temperature, door type, pressure, and size of the anteroom are factors that are effective on the safety of the hospital environment. Studies demonstrated that providing an anteroom for changing clothing and storing equipment may be useful in reducing the transmission of airborne infections in hospitals. Since the transmission route of SARS-CoV2 is common with other respiratory infectious agents, it can be concluded that a well-designed anteroom could potentially decrease the risk of SARS-CoV2 transmission during hospitalization as well.

The effect of door opening on air-mixing in a positively pressurized room: Implications for operating room air management during the COVID outbreak

The effect of the built environment on the predominant indoor airflow patterns is significant. To protect the healthcare workers at the front line from the outbreak of COVID − 19, it is necessary to understand the transmission dynamics of the virus, which has been shown to depend on indoor airflow patterns. In hospital operating rooms (ORs), design requirements pose a unique challenge as the positive pressure in the OR can facilitate virus spread into adjacent spaces, shall a COVID-positive patient require a surgical procedure. Moreover, the turbulent vortexes from door motions could independently increase the probability of virus escape from the OR to the adjacent corridors. Therefore, to obtain critical knowledge about the alteration of flow fields due to door movement in a positively pressurized room and quantify the air mixing across the door, a series of experiments were conducted in a controlled chamber. The results demonstrate significant impacts of the door opening on the airflow patterns. Increased alterations near the door and vortexes penetrating far into the chamber with multiple doors openings warrant further study of the indoor airflow dynamic under door motion. This experimental study proposes an algorithm to quantify the air exchange due to a standard door opening and quantifies this exfiltration of contaminated air up to 2 air changes per hour, that is 10% of the chamber supply airflow rate. The algorithm to quantify the dissipated air quantity and the analyses of interaction between initial conditions and door openings contribute to the originality of this paper.

Dispersion of virus-laden droplets in ventilated rooms: Effect of homemade facemasks

In December 2019, the SARS-CoV-2 virus emerged and rapidly spread throughout the world. It causes the respiratory disease COVID-19 via the transmission of microbial pathogens within bio-aerosols during speaking, sneezing, and coughing. Therefore, understanding bioaerosol dynamics is important for developing mitigation strategies against droplet-induced infections. Computer modelling, using Computational Fluid Dynamics, has become a useful tool in studying and visualising the spread of atomised bio-droplets but the effect of using cloth facemasks has not been fully quantified. In this study, simulations were carried out to quantify the extent of respiratory droplet transfer with and without facemasks between a pair of ventilated rooms by a mathematical model for the first time. A 600-μm pore facemask was used, representing the porosity of a typical cloth facemask. Using the discrete phase model, the transport of ejected droplets was tracked. The results show that in the facemask cases, more than 96% of all the ejected droplets in all scenarios were trapped in the recommended 2 m social distancing radius around the human source. Correspondingly, only a maximum of 80% of droplets were deposited within the social distancing radius in the no facemask scenarios, with >20% airborne and transported to the second room. One-dimensional empirical correlations were developed for droplet concentration as a function of distance from the bioaerosol source. The models show that droplet concentration decays exponentially from the source especially in the facemask cases. The study therefore reinforces the importance of face coverings in lessening the transmission of possibly infected respiratory droplets that transmit highly infectious diseases such as COVID-19.

Novel measurement system for respiratory aerosols and droplets in indoor environments

The SARS-CoV-2 pandemic has created a great demand for a better understanding of the spread of viruses in indoor environments. A novel measurement system consisting of one portable aerosol-emitting mannequin (emitter) and a number of portable aerosol-absorbing mannequins (recipients) was developed that can measure the spread of aerosols and droplets that potentially contain infectious viruses. The emission of the virus from a human is simulated by using tracer particles solved in water. The recipients inhale the aerosols and droplets and quantify the level of solved tracer particles in their artificial lungs simultaneously over time. The mobile system can be arranged in a large variety of spreading scenarios in indoor environments and allows for quantification of the infection probability due to airborne virus spreading. This study shows the accuracy of the new measurement system and its ability to compare aerosol reduction measures such as regular ventilation or the use of a room air purifier.

Emissions, airflow patterns and modeling of test compounds in controlled hospital environments

Spreading and distribution of selected volatile organic compounds (VOCs) released as point source emissions in a hospital environment were investigated in two office rooms and two patient rooms. Six tracer compounds were released from six locations and their concentrations were measured in five sampling sites during two consecutive days. The air flow rates, velocity and flow direction, air temperature, pressure differences between adjacent rooms, and relative humidity and concentrations of the tracer compounds were measured. The results revealed that the size of the examined space and ventilation rates, the monitoring point should be either close to the exhaust terminal device or in the middle of the occupied zone the way that supply air flows do not interfere the measurements. Depending on the inlet terminal device and its location, the air is either delivered parallel to the ceiling or it can be directed to a desired spot into the occupied zone. The tracer compounds did spread evenly within the room and their concentrations decreased inversely with the distance. In rooms with a good ventilation, the concentrations at the exhaust air terminal units were close to those measured near the source point. The results obtained from modeling were consistent with the measurements.

Reducing Morbidity and Mortality Rates from COVID-19, Influenza and Pneumococcal Illness in Nursing Homes and Long-Term Care Facilities by Vaccination and Comprehensive Infection Control Interventions

The COVID-19 pandemic identifies the problems of preventing respiratory illnesses in seniors, especially frail multimorbidity seniors in nursing homes and Long-Term Care Facilities (LCTFs). Medline and Embase were searched for nursing homes, long-term care facilities, respiratory tract infections, disease transmission, infection control, mortality, systematic reviews and meta-analyses. For seniors, there is strong evidence to vaccinate against influenza, SARS-CoV-2 and pneumococcal disease, and evidence is awaited for effectiveness against COVID-19 variants and when to revaccinate. There is strong evidence to promptly introduce comprehensive infection control interventions in LCFTs: no admissions from inpatient wards with COVID-19 patients; quarantine and monitor new admissions in single-patient rooms; screen residents, staff and visitors daily for temperature and symptoms; and staff work in only one home. Depending on the vaccination situation and the current risk situation, visiting restrictions and meals in the residents' own rooms may be necessary, and reduce crowding with individual patient rooms. Regional LTCF administrators should closely monitor and provide staff and PPE resources. The CDC COVID-19 tool measures 33 infection control indicators. Hand washing, social distancing, PPE (gowns, gloves, masks, eye protection), enhanced cleaning of rooms and high-touch surfaces need comprehensive implementation while awaiting more studies at low risk of bias. Individual ventilation with HEPA filters for all patient and common rooms and hallways is needed.

Sensitivity analysis of influence factors on multi-zone indoor airflow CFD simulation

Computational fluid dynamics (CFD) is a powerful tool for performing indoor airflow analysis. The simulation results are usually validated with measurement results for accuracy in reflecting reality. When conducting CFD for simulating air flow in a multiple-zone indoor environment with different boundary conditions in different regions, the validation of the CFD model becomes sophisticated. To improve the accuracy of the simulation, boundary conditions need to be adjusted based on how significant the influence factors are affecting the multi-zone CFD model, which few studies have been conducted on. The objective of this study is to investigate the impact of influence factors on temperature and carbon dioxide concentration distribution of a validated CFD model of a typical office floor using ANSYS Fluent. This study provides insights on how to fine-tune a complex model to reflect the actual air flow and how the air quality and human comfort in different zones on the same floor could be affected by influence factors. The influence factors investigated are: (1) size of door gaps, (2) solar radiation and (3) number and orientation of occupants. The velocity variations caused by different door gap sizes were studied for improving multi-zone simulation accuracy by adjusting door gap sizes. To study the significant impact of solar heat on multi-zone environment, the sensitivity of different regions of the office floor to solar heat amount and distribution was analyzed by conducting solar analysis under different weather conditions. Impact of occupants on temperature and carbon dioxide concentration distributions in multi-zone environment were investigated by considering different numbers and facing directions of occupants in different regions of the office floor. In addition, this study demonstrates how to modify the influence factors efficiently using building information modeling (BIM).

Performance analysis of portable HEPA filters and temporary plastic anterooms on the spread of surrogate coronavirus

The outbreak of COVID-19, and its current resurgence in the United States has resulted in a shortage of isolation rooms within many U.S. hospitals admitting COVID-19-positive cases. As a result, hospital systems, especially those at an epicenter of this outbreak, have initiated task forces to identify and implement various approaches to increase their isolation capacities. This paper describes an innovative temporary anteroom in addition to a portable air purifier unit to turn a general patient room into an isolation space. Using an aerosolization system with a surrogate oil-based substance, we evaluated the effectiveness of the temporary plastic anteroom and the portable air purifier unit. Moreover, the optimal location of the portable unit, as well as the effect of negative pressurization and door opening on the containment of surrogate aerosols were assessed. Results suggested that the temporary anteroom alone could prevent the migration of nearly 98% of the surrogate aerosols into the adjacent corridor. Also, it was shown that the best location of a single portable air purifier unit is inside the isolation room and near the patient's bed. The outcome of this paper can be widely used by hospital facilities managers when attempting to retrofit a general patient room into an airborne infection isolation room.

How Can Design Features and Other Factors Affect the Indoor Air Quality in Inpatient Rooms? Check-Lists for the Design Phase, Daily Procedures and Maintenance Activities for Reducing the Air Concentrations of Chemical Pollution

Indoor Air Quality (IAQ) is one of main topics of Public Health on which international institutions and countries are taking action. With regards to healing architectures, several studies have reported data analysis and case studies to improve users' health (patients, and medical and administrative staffs), but there are not enough regarding volatile organic compounds (VOCs). Regarding chemical pollution of indoor air, the Scientific Community has highlighted that there are several factors that affect the IAQ, in particular the design and management, and energetic efficiency, of inpatient wards. Several stakeholders, from the designers to the managers, are responsible for the indoor air in healing environments. Supported by analysis of the State of the Art and the main factors that influence the heterogeneous scenario of inpatient wards, the paper presents three check-lists, designed for supporting the stakeholders during the design phase, or for the daily procedures and maintenance activities, for pre-assessment of factors that affect chemical pollution, and for the definition of strategies to be applied. In fact, in such environments IAQ assumes a particular meaning and importance, both for the vulnerability of the patients and for the long time spent by the sanitary staff. The multidisciplinary approach emphasizes the continuous need for interdisciplinary knowledge and skills aimed at finding solutions able to protect users' health status (including patients, workers and visitors), especially in the field of the indoor air issue.

The Influence of Surgical Staff Behavior on Air Quality in a Conventionally Ventilated Operating Theatre during a Simulated Arthroplasty: A Case Study at the University Hospital of Parma

Surgical staff behavior in operating theatres is one of the factors associated with indoor air quality and surgical site infection risk. The aim of this study was to apply an approach including microbiological, particle, and microclimate parameters during two simulated surgical hip arthroplasties to evaluate the influence of staff behavior on indoor air quality. During the first hip arthroplasty, the surgical team behaved correctly, but in the second operation, behavioral recommendations were not respected. Microbiological contamination was evaluated by active and passive methods. The air velocity, humidity, temperature, and CO2 concentration were also monitored. The highest levels of microbial and particle contamination, as well as the highest variation in the microclimate parameter, were recorded during the surgical operation where the surgical team behaved "incorrectly". Turbulent air flow ventilation systems appeared more efficient than in the past and very low air microbial contamination was reached when behavior was correct. Therefore, adherence to behavioral recommendations in operating theatres is essential to not undermine the effectiveness of the heating, ventilation, and air conditioning systems and employed resources.

Checklist for infection control in the emergency department

The risk of encountering human-to-human infections, including emerging infectious diseases, should be adequately and appropriately addressed in the emergency department. However, guidelines based on sufficient evidence on infection control in the emergency department have not been developed anywhere in the world. Each facility examines and implements its own countermeasures. The Japanese Association for Acute Medicine has established the "Committee for Infection Control in the Emergency Department" in cooperation with the Japanese Association for Infectious Diseases, Japanese Society for Infection Prevention and Control, Japanese Society for Emergency Medicine, and Japanese Society for Clinical Microbiology. A joint working group has been established to consider appropriate measures. This group undertook a comprehensive and multifaceted review of infection control measures for emergency outpatients and related matters, and released a checklist for infection control in emergency departments. This checklist has been prepared such that even small emergency departments with few or no emergency physicians can control infection by following the checklist, without committing any major errors. The checklist includes a control system for infection control, education, screening, and vaccination, prompt response to suspected infections, and management of the risk of infection in facilities. In addition, the timing of the check and interval at which the check is carried out are specified as categories. We hope that this checklist will contribute to improving infection control in the emergency department.

Large-eddy simulation of the containment failure in isolation rooms with a sliding door-An experimental and modelling study

In hospital isolation rooms, door operation can lead to containment failures and airborne pathogen dispersal into the surrounding spaces. Sliding doors can reduce the containment failure arising from the door motion induced airflows, as compared to the hinged doors that are typically used in healthcare facilities. Such airflow leakage can be measured quantitatively using tracer gas techniques, but detailed observation of the turbulent flow features is very difficult. However, a comprehensive understanding of these flows is important when designing doors to further reduce such containment failures. Experiments and Computational Fluid Dynamics (CFD) modelling, by using Large-Eddy Simulation (LES) flow solver, were used to study airflow patterns in a full-scale mock-up, consisting of a sliding door separating two identical rooms (i.e. one isolation room attached to an antechamber). A single sliding door open/ hold-open/ closing cycle was studied. Additional variables included human passage through the doorway and imposing a temperature difference between the two rooms. The general structures of computationally-simulated flow features were validated by comparing the results to smoke visualizations of identical full-scale experimental set-ups. It was found that without passage the air volume leakage across the doorway was first dominated by vortex shedding in the wake of the door, but during a prolonged hold-open period a possible temperature difference soon became the predominant driving force. Passage generates a short and powerful pulse of leakage flow rate even if the walker stops to wait for the door to open.

ELECTRONIC SUPPLEMENTARY MATERIAL ESM

supplementary material is available in the online version of this article at 10.1007/s12273-017-0422-8.

Implementing a negative-pressure isolation ward for a surge in airborne infectious patients

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A 30-bed negative-pressure isolation ward was established on a functioning hospital.

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The pressure relative to the main hospital was −29 Pa by adjusting the ventilation.

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No occurrences of pressure reversal occurred at ward entrance.

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Pressures on the ward changed to slightly positive.

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Health care personnel should wear personal protective equipment on the ward.

Background

During a large-scale airborne infectious disease outbreak, the number of patients needing hospital-based health care services may exceed available negative-pressure isolation room capacity.

Methods

To test one method of increasing hospital surge capacity, a temporary negative-pressure isolation ward was established at a fully functioning hospital. Negative pressure was achieved in a 30-bed hospital ward by adjusting the ventilation system. Differential pressure was continuously measured at 22 locations, and ventilation airflow was characterized throughout the ward.

Results

The pressure on the test ward relative to the main hospital hallway was −29 Pa on average, approximately 10 times higher than the Centers for Disease Control and Prevention guidance for airborne infection control. No occurrences of pressure reversal occurred at the entrances to the ward, even when staff entered the ward. Pressures within the ward changed, with some rooms becoming neutrally or slightly positively pressurized.

Conclusions

This study showed that establishing a temporary negative-pressure isolation ward is an effective method to increase surge capacity in a hospital.