CFD modelling of airborne virus diffusion characteristics in a negative pressure room with mixed mode ventilation

Abstract

COVID-19 caused by severe acute respiratory syndrome (SARS) has accounted for huge collateral damage and as the virus is spreading faster and faster this study deals with isolation rooms or negative pressure rooms with 12 or more air changes per hour and maintaining a pressure difference of 2.5 pa which can help in reducing the transmission of the virus from affected to not affected persons. ANSI/ASHRAE/ASHE Standard 170–2008 recommendations are followed for hospital applications, to facilitate effective ventilation. These negative pressure rooms prevent the spread of the contaminated particles to the surroundings and by creating a negative pressure in the room whenever the door is opened the atmospheric air is sucked in and not the one which is present inside the room. The Computational fluid dynamics simulations are performed to investigate the diffusion of airbone virus inside a negative pressure room with mixed mode ventilation system. It was identified that the mixed mode ventilation system is more effective in controlling the spread of virus droplets inside the room

Current approaches for preventing environment-associated contamination in healthcare facilities: a systematic literature review by open access database

“…Ventilation type (central air-conditioning system or non-central air conditioning system), increased visitor and doctors’ activities, and cleaning sessions also interfere with indoor air quality [ 15 ] Necessity of increasing the rate of air change, decreasing recirculation of air, increasing the use of outdoor air and HEPA filters for disease and infection control [ 30 ] Indoor air temperature, relative humidity, indoor ventilation rate, air filtration system, differential pressure control, and mechanical strategies are related to patient medical outcomes [ 3 ] Necessity of increasing air supply and exhaust ventilation on toilets to avoid the fecal–oral transmission due to the droplets generated when flushing with the toilet lid open [ 27 ] The air exchange rate, the location of an infected patient, and the location of exhaust grilles in a ward influence the extent of the contamination. Generally, it is recommended that exhaust grilles are placed above each patient's bed [ 29 ] Airflow patterns, distribution of aerosol particles, and thermal comfortability in patient rooms depend on several factors such as the presence and type of air conditioner, the location of fresh air diffusers, the location of room return, and the flow rate of fresh air diffusers [ 16 , 21 , 26 , 31 , 34 , 37 ] Airborne infection isolation rooms or isolation spaces (with negative pressure) are crucial for the control of acute respiratory infectious threats. The plan of these rooms includes many decisions: mechanical ventilation system specifications, location, layout, interior finishing, facilities, and return air, exhaust air, and supply air locations Disinfection and hygiene [ 41 ] Importance of developing mechanisms and equipment to protect healthcare professionals and other users in the face of COVID-19 tests.…”

The airflow distribution and aerosol diffusion rules in the negative pressure isolation ward

“…Ling et al 14 regarded SF6 as a tracer gas to explore the contaminant discharge efficiency of the negative pressure isolation ward under different forms of airflow distribution. Berlanga et al 15 experimentally The influence of airflow in the indoor environment on the distribution and transmission of droplets when infected persons talk and cough Ren et al 3 The flow field, flow structures, and particle trajectories of three ventilation strategies Wang et al 4 Optimize the air distribution in a hospital ward Anuraghava et al 5 The diffusion of airborne virus was studied in a negative pressure room with a mixed ventilation system Lu and Lin 6 The characteristics of coughed droplet dispersion in hospital wards under stratum ventilation Erdogan and Yilmazoglu 7 The aerosol distribution characteristics, airflow patterns, and temperature distribution characteristics of three different ventilation strategies (conventional, switched and local exhaust) Dao and Kim 8 The effects of different air outlet locations on the removal efficiency of infectious droplets in isolation chamber Niu et al 9 The effects of mixing ventilation and perforated ceiling air supplying ventilation on aerosol diffusion and deposition Alkhalaf et al 10 Four designs with three airflows, 9, 12, and 15 ACH (Air Change per Hour) were used to explore the capacity of the ventilation system to remove contaminant Tan et al 11 Airflow and particle dispersion under a baseline case and four proposed ventilation strategies Qian et al 12 Experiment research…”

“…Wang et al 4 evaluated the proposed ten air distributions in terms of total maximum time (TMT) and total particle concentration (OPC) to derive a relatively optimized airflow scheme, which is of guiding significance for the restructuring of specialized respiratory infectious disease wards in the hospital. Anuraghava et al 5 identified that the mixed mode ventilation system could control the spread of virus droplets in the room more effectively. Lu and Lin 6 investigated the dynamic process of the coughed droplets dispersion and the spatial distribution of the droplets in a two-bed hospital ward under stratum ventilation, and compared it with displacement ventilation and mixing ventilation.…”

A vertical laminar airflow system to prevent aerosol transmission of SARS-CoV-2 in building space: Computational fluid dynamics (CFD) and experimental approach

“…On the other hand, many recent COVID-related findings reveal that airborne transmission is a significant potential or primary cause of the infection spread in general settings. [3][4][5][6][7] In the fluidic transmission, infection is occurred by a passage of virus-laden particulates (aerosols) -fine solid or liquid droplet nuclei less than 5 μm in diameter. 8,9 Due to their very small sizes and weights, aerosols containing pneumonitic microbes or virus sources can remain active in the air for a long period of time (>3 h 10 ) and a greater distance (>10 m away from emission sources 11 ).…”