Numerical investigation of airborne transmission of respiratory infections on the subway platform

Underground subway platforms are among the world’s busiest public transportation systems,but the airborne transmission mechanism of respiratory infections on these platforms has been rarely studied.Here,computational fluid dynamics(CFD)modeling is used to investigate the airflow patterns and infection risks in an island platform under two common ventilation modes:Mode 1-both sides have air inlets and outlets;Mode 2-air inlets are present at the two sides and outlets are present in the middle.Under the investigated scenario,airflow structure is characterized by the ventilation jet and human thermal plumes.Their interaction with the infector’s breathing jet imposes the front passenger under the highest exposure risk by short-range airborne route,with intake fractions up to 2.57%(oral breathing)or 0.63%(nasal breathing)under Mode 1;oral breathing of the infector may impose higher risks for the front passenger compared with nasal breathing.Pathogen are efficiently diluted as they travel further,in particular to adjacent crowds.The maximum and median value of intake fractions of passengers in adjacent crowds are respectively 0.093%and 0.016%(oral breathing),and 0.073%and 0.014%(nasal breathing)under Mode 1.Compared with Mode 1,the 2nd mode minimizes the interaction of ventilation jet and breathing jet,where the maximum intake fraction is only 0.34%,and the median value in the same crowd and other crowds are reduced by 23–63%.Combining published quanta generation rate data of COVID-19 and influenza infectors,the predicted maximum and median infection risks for passengers in the same crowds are respectively 1.46%–40.23%and 0.038%–1.67%during the 3–10 min waiting period,which are more sensitive to ventilation rate and exposure time compared with return air.This study can provide practical guidance for the prevention of respiratory infections in subway platforms.

The airborne contagiousness of respiratory viruses:A comparative analysis and implications for mitigation

The infectious emission rate is a fundamental input parameter for airborne transmission risk assessment,but data are limited due to reliance on estimates from chance superspreading events.This study assesses the strength of a predictive estimation approach developed by the authors for SARS-CoV-2 and uses novel estimates to compare the contagiousness of respiratory pathogens.We applied the approach to SARS-CoV-1,SARS-CoV-2,MERS,measles virus,adenovirus,rhinovirus,coxsackievirus,seasonal influenza virus and Mycobacterium tuberculosis(TB)and compared quanta emission rate(ER)estimates to literature values.We calculated infection risk in a prototypical classroom and barracks to assess the relative ability of ventilation to mitigate airborne transmission.Our median standing and speaking ERestimate for SARS-CoV-2(2.7 quanta h)is similar to active,untreated TB(3.1 quanta h),higher than seasonal influenza(0.17 quanta h-1),and lower than measles virus(15 quanta h).We calculated event reproduction numbers above 1 for SARS-CoV-2,measles virus,and untreated TB in both the classroom and barracks for an activity level of standing and speaking at low,medium and high ventilation rates of 2.3,6.6 and 14 L per second per person(L sp),respectively.Our predictive ERestimates are consistent with the range of values reported over decades of research.In congregate settings,current ventilation standards are unlikely to control the spread of viruses with upper quartile ERqvalues above 10 quanta h,such as SARS-CoV-2,indicating the need for additional control measures.

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/m^(3))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.

A Preliminary Numerical Investigation of Airborne Droplet Dispersion in Aircraft Cabins

The emergence of the novel coronavirus has led to a global pandemic which has led to the airline industry facing severe losses. For air travel to recover, airlines need to ensure safe air travel. In this paper, the authors have modeled droplet dispersion after a single breath from an index patient. Computational Fluid Dynamics (CFD) simulations are conducted using the k-ωSST turbulence model in ANSYS Fluent. The authors have taken into consideration several parameters such as the size of the mouth opening, the velocity of the cabin air as well as the number of droplets being exhaled by the index patient to ensure a realistic simulation. Preliminary results indicate that after a duration of 20 s, droplets from the index patient disperse within a 10 m2 cabin area. About 75% of the droplets are found disperse for up to 2 m axially behind the index patient. This could possess an enhanced risk to passengers sitting behind the index patient. Ultimately, this paper provides an insight into the potential of CFD to visualise droplet dispersal and give impetus to ensure that necessary mitigating measures can be taken to reduce the risk of infection through droplet dispersal.

Assessment of SARS-CoV-2 airborne infection transmission risk in public buses

Public transport environments are thought to play a key role in the spread of SARS-CoV-2 worldwide.Indeed,high crowding indexes(i.e.high numbers of people relative to the vehicle size),inadequate clean air supply,and frequent extended exposure durations make transport environments potential hotspots for transmission of respiratory infections.During the COVID-19 pandemic,generic mitigation measures(e.g.physical distancing)have been applied without also considering the airborne transmission route.This is due to the lack of quantified data about airborne contagion risk in transport environments.In this study,we apply a novel combination of close proximity and room-scale risk assessment approaches for people sharing public transport environments to predict their contagion risk due to SARS-CoV-2 respiratory infection.In particular,the individual infection risk of susceptible subjects and the transmissibility of SARS-CoV-2(expressed through the reproduction number)are evaluated for two types of buses,differing in terms of exposure time and crowding index:urban and long-distance buses.Infection risk and reproduction number are calculated for different scenarios as a function of the ventilation rates(both measured and estimated according to standards),crowding indexes,and travel times.The results show that for urban buses,the close proximity contribution significantly affects the maximum occupancy to maintain a reproductive number of<1.In particular,full occupancy of the bus would be permitted only for an infected subject breathing,whereas for an infected subject speaking,masking would be required.For long-distance buses,full occupancy of the bus can be maintained only if specific mitigation solutions are simultaneously applied.For example,for an infected person speaking for 1 h,appropriate filtration of the recirculated air and simultaneous use of FFP2 masks would permit full occupancy of the bus for a period of almost 8 h.Otherwise,a high percentage of immunized persons(>80%)would be needed.

Airborne Acoustic Transmission and Terrain Topography at SAINTGITS Amphitheatre:An Analysis of Outdoor Auditory Perception and Comparison of Contour Plots

The arrangement of natural and physical features on the earth’s surface are a few among the countless items that govern the airborne acoustic transmission at boundary layers.In particular,if the acoustic waves are attributes of live concerts at open-air theatres,without losing the sheen and quality,the audience should certainly receive the unbroken depth of the performance.Hence,at all times,it is advisable to analyse the auditory receptiveness,particularly in all intended recreational spaces.The current pandemic circumstances and the mandated COVID-19 prevention protocols encourage gatherings in naturally ventilated outdoor regions than confined indoors.This work predicts and quantifies the acoustic experience at the naturally carved amphitheatre at SAINTGITS,an autonomous institution at the down South-West of the Indian Subcontinent.The entire recreational space at SAINTGITS AMPHI was separately modelled as a Base case and Advanced case,and were analysed using the acoustic modelling module of EASE Focus,a renowned simulation freeware,which is in strict adherence with the International standards.The variation in loudness received at the nearest and farthest ends of the amphitheatre was between 67 to 80 dB.Though the Zero frequency SPL(Z-weighting)exhibited the loudness in the range of 81 to 85 dB and could maintain a safer auditory level for any human ear,it was confined to a hemispherical region near the sound source.A vertical beam angle of−4.0°was found to be effective throughout.The procedures and analyses will certainly help the future organizers and stakeholders to effectively plan the resources to reap rich acoustic experience at terrain-centric locales.The surface topography and contours were plotted with another set of freeware,the CADMAPPER and the QUIKGRID,to compare terrain gradient with the known data.Furthermore,this interdisciplinary research exhibits the extensive simulation capability of both EASE Focus and QUIKGRID and demonstrates the modelling versatility and deliverable potential of these freeware to benefit the budding architects and researchers.

Vented Individual Patient(VIP)Hoods for the Control of Infectious Airborne Diseases in Healthcare Facilities

By providing a means of separating the airborne emissions of patients from the air breathed by healthcare workers(HCWs),vented individual patient(VIP)hoods,a form of local exhaust ventilation(LEV),offer a new approach to reduce hospital-acquired infection(HAI).Results from recent studies have demonstrated that,for typical patient-emitted aerosols,VIP hoods provide protection at least equivalent to that of an N95 mask.Unlike a mask,hood performance can be easily monitored and HCWs can be alerted to failure by alarms.The appropriate use of these relatively simple devices could both reduce the reliance on personal protective equipment(PPE)for infection control and provide a low-cost and energy-efficient form of protection for hospitals and clinics.Although the development and deployment of VIP hoods has been accelerated by the coronavirus disease 2019(COVID-19)pandemic,these devices are currently an immature technology.In this review,we describe the state of the art of VIP hoods and identify aspects in need of further development,both in terms of device design and the protocols associated with their use.The broader concept of individual patient hoods has the potential to be expanded beyond ventilation to the provision of clean conditions for individual patients and personalized control over other environmental factors such as temperature and humidity.

Performance of personalized ventilation in mitigating short-range airborne transmission under the influence of multiple factors

The effectiveness of using personalized ventilation(PV)in mitigating airborne transmission risk was found to be easily affected by multiple factors.The aim of this study was hereby to evaluate the impacts of several important factors on the performance of PV in airborne disease control for closely ranged occupants.Orthogonal experiments were designed for CFD simulations under different levels of four selected factors.Results indicated that the order of significance of these four factors affecting the intake fraction(IF)of the exposed occupant was as follows:mode of PV use>relative distance between occupants>PV airflow volume>background ventilation.The best combination of the four tested factors was PV of 15 L/s for both the infected source and the exposed occupant,with a relative distance of 2 m between them and mixing ventilation,which would yield an IF of merely 0.0246%.The worst combination was PV of 6 L/s for the exposed occupant only,with a relative distance of 0.86 m under displacement ventilation,indicating an elevated IF of 0.2919%.The increase of PV air volume and relative separation distance both contributed to lower exposure risk,but they were not as influential as the mode of PV use.PV integrated with mixing ventilation and utilized for both infected and susceptible occupants were recommended.The findings in this study will be helpful to provide guidance for the implementation of PV in indoor environment for airborne infection control.

Airborne transmission of virus-laden droplets in an aircraft cabin

This study investigates the airborne transmission of virus-laden droplets generated by a cough of patients in an aircraft cabin to reveal the infection risk of taking an airplane.The influence of the ventilation system on the flow feld of the cabin was analysed to reveal its effects on the airbore transmission ofvirus-laden droplets.Meanwhile.human body heat was also considered in the simulations.The results show that hot plume due to human body hent has a significant impact on the upward movement of virus-laden droplets.The virus-laden droplets expelled by a cough can be transmitted to the region two to three rows away from the generator.Particularly,the transverse motion present in the early stage of the droplet transmission results in a high infection risk to the passengers in the same row as the patient.This work gives insight into the understanding of the airborne transmission of virus-laden droplets in the entire passenger cabin.

Leakage versus Material Filtration in Barrier Facemask Efficiency

The World Health Association and many governmental agencies recommend the wearing of facemasks by the general public to prevent the spread of COVID-19. It is believed that masks can significantly protect others and may offer some protection to the wearer. Although there are standards for FFRs, surgical masks, and recently for barrier face coverings, they all indicate the level of protection for the wearer. However, testing facial masks not at the point of inhalation, but at the source, the exhale, offers a new perspective on how to impede particle emissions. In this paper, the experimental results show that, although the barrier face covering is less effective than FFRs or surgical masks, it can reduce the concentration of aerosols downstream of the device. The results on barrier efficiency show a rapid decrease in effectiveness when the face covering is not sealed to the head. The barrier efficiency of two of the barrier face coverings tested is strongly dependent on leakage caused by the fit rather than the material. While some materials certainly are more effective than others in inhibiting particle penetration, an even more profound factor is the amount of leakage emitted from a mask. New approaches to fit and design in order to create a seal against leakage will become an important factor in combatting SARS-CoV-2.

Laboratory studies on the infectivity of human respiratory viruses:Experimental conditions,detections,and resistance to the atmospheric environment

The environmental stability of infectious viruses in the laboratory setting is crucial to the transmission potential of human respiratory viruses.Different experimental techniques or conditions used in studies over the past decades have led to diverse understandings and predictions for the stability of viral infectivity in the atmospheric environment.In this paper,we review the current knowledge on the effect of simulated atmospheric conditions on the infectivity of respiratory viruses,mainly focusing on influenza viruses and coronaviruses,including severe acute respiratory syndrome coronavirus 2 and Middle East respiratory syndrome coronavirus.First,we summarize the impact of the experimental conditions on viral stability;these involve the methods of viral aerosol generation,storage during aging and collection,the virus types and strains,the suspension matrixes,the initial inoculum volumes and concentrations,and the drying process.Second,we summarize and discuss the detection methods of viral infectivity and their disadvantages.Finally,we integrate the results from the reviewed studies to obtain an overall understanding of the effects of atmospheric environmental conditions on the decay of infectious viruses,especially aerosolized viruses.Overall,this review highlights the knowledge gaps in predicting the ability of viruses to maintain infectivity during airborne transmission.

Research and development of prevention and control measures on the transmission of pathogens in compartments of passenger transport

Contagious pathogens like COVID-19 transmitted via respiratory droplets spread effortlessly in the passenger compartments of transport,significantly jeopardizing passengers’safety when taking public transportation.To date,studies on the fundamental theories of airborne droplet transmission and the engineering application of decontamination techniques are insufficient for the prevention and control of pathogens transmitting in the compartments of passenger transport.It is essential to systematically investigate the control approaches to restrain pathogens from transmitting in passenger compartments.Herein,a theoretical framework for calculating the transmission of pathogens in a complex compartment environment was proposed,and experimental platforms that satisfy the Biosafety Level-2 Laboratory safety level for compartment environment simulations were built based on a set of real train cabins.On these bases,numerical investigations on the motion of pathogen-laden droplets were conducted,and decontamination techniques were examined experimentally.Thereby,control measures on the pathogen transmission and pathogen decontamination schemes were proposed.Moreover,highly efficient decontamination devices were developed,and coping strategies for epidemic emergencies were devised.The outcomes provide theoretical and technical support for developing the next generation of transportation and the prevention and control measures cooperatively considering regular and pandemic times.

AWells-Riley/based COVID-19 infectiousrisk assessment model combining both short rangeandroom scale effects

There is growing evidence of the high transmission potential of COVID-19 through virus-laden aerosols.Because aerosols are inhaled in various concentrations,an overall assessment of transmission risks at different indoor scales is crucial.However,a comprehensive risk assessment method that evaluates the direct link between short-range and room-scale zones is stl lacking.In this paper,a risk assessment model combining both short-range and room-scale effects is developed to obtain effective reproduction number in confined indoor environments,called Turbulent Jet Wells Riley(TJWR)model.Combined with the viral load data and aerosol generation data of different human respiratory activities,the Monte Carlo simulation method is applied to calculate the quanta emission rate,which further provides the input parameters of the TJWR model.Three known outbreaks(Hangzhou banquet hall X,Guangzhou restaurant Y,and Hong Kong restaurant Z,China)are chosen to validate the TJWR model.Results show that the TJWR model is more efficient than the original Wells-Riley model.The average relative error of the TJWR model ranges between 9%and 44%,while for the Wells-Riley model,it ranges between 57%and 78%.The TJWR model also proves that infection risk assessments using the well-mixed assumption can systematically underestimate the transmission risk for those close to the source.Additionally,there is a significant positive linear correlation between the total number of exposed individuals at the short-range and the effective reproduction number.This newly developed TJWR model has great potential for rapid and real-time overall airborne transmission risk assessment in buildings and cities.

Airborne transmission during short-term events: Direct route over indirect route

Numerous short-term exposure events in public spaces were reported during the COVID-19 pandemic,especially during the spread of Delta and Omicron.However,the currently used exposure risk assessment models and mitigation measures are mostly based on the assumption of steady-state and complete-mixing conditions.The present study investigates the dynamics of airborne transmission in short-term events when a steady state is not reached before the end of the events.Large-eddy simulation(LES)is performed to predict the airborne transmission in short-term events,and three representative physical distances between two occupants are examined.Both time-averaged and phase-averaged exposure indices are used to evaluate the exposure risk.The results present that the exposure index in the short-term events constantly varies over time,especially within the first 1/ACH(air changes per hour)hour of exposure between occupants in close proximity,posing high uncertainty to the spatial and temporal evolutions of the risk of cross-infection.The decoupling analysis of the direct and indirect airborne transmission routes indicates that the direct airborne transmission is the predominated route in short-term events.It suggests also that the general dilution ventilation has a relatively limited efficiency in mitigating the risk of direct airborne transmission,but determines largely the occurrence time of the indirect one.Given the randomness,discreteness,localization,and high-risk characteristics of direct airborne transmission,a localized method that has a direct interference on the respiratory flows would be better than dilution ventilation for short-term events,in terms of both efficiency and cost.

The assessment of personal exposure in restaurants considering heat sources and ventilation strategies

Outbreaks of airborne infections during meal consumption in diverse restaurant settings have been extensively reported.It is widely recognized that effective ventilation strategies are essential to minimize the infection risk in indoor environments,and these strategies should be tailored to the heat sources.The purpose of this study is to compare the spatial distribution of risk in restaurant rooms that use mixing or displacement ventilation,specif-ically focusing on the heat sources used for different food types,namely hotpot,normal Chinese food,and iced food.Computational Fluid Dynamics(CFD)was employed to assess exposure risk.Our results indicate that the use of low-temperature heat sources can elevate the risk of infection by increasing the local vertical temperature gradient.In comparison to no heat source,the risk increased by 190.9%and 99.6%for displacement and mixing ventilation strategies,respectively.Under mixing ventilation,both low-temperature and no heat sources showed lower infection risks when compared to displacement ventilation.However,displacement ventilation is found to be highly effective in reducing the risk of infection when using a high-temperature heat source,with only 12.3%of the infection risk observed in mixing ventilation.Furthermore,the use of displacement ventilation resulted in a significant reduction in the odors emitted by hotpot,which were instead absorbed by clothes in the mixing ven-tilation scenario.Our findings provide crucial insights into the development of appropriate ventilation strategies for reducing personal exposure to airborne infections in diverse restaurant settings.Specifically,we recommend using displacement ventilation in restaurants that utilize high-temperature heat sources,as it can substantially reduce the risk of infection.

Predominance of inhalation route in short-range transmission of respiratory viruses:Investigation based on computational fluid dynamics

During the coronavirus disease 2019 pandemic,short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission.However,the roles played by the inhalation and large droplet routes cannot be distinguished in practice.A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections.In the current study,short-range exposure was analyzed via computational fluid dynamics(CFD)simulations using a discrete phase model.Detailed facial membranes,including eyes,nostrils,and a mouth,were considered.In CFD simulations,there is no need for a spherical approximation of the human head for estimating deposition nor the“anisokinetic aerosol sampling”approximation for estimating inhalation in the analytical model.We considered two scenarios(with two spheres[Scenario 1]and two human manikins[Scenario 2]),source-target distances of 0.2 to 2 m,and droplet diameters of 3 to 1,500μm.The overall CFD exposure results agree well with data previously obtained from a simple analytical model.The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50μm during talking and coughing.A critical droplet size of 87.5μm was found to differentiate droplet behaviors.The number of droplets deposited on the target head exceeded those exposed to facial membranes,which implies a risk of exposure through the immediate surface route over a short range.

Tracing the origin of large respiratory droplets by their deposition characteristics inside the respiratory tract during speech

Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments.Transient talking activities characterized by low(0.2 L/s),medium(0.9 L/s),and high(1.6 L/s)airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics(CFD)simulations based on a real human airway model.SST k-ωmodel was chosen to predict the airflow field,and the discrete phase model(DPM)was used to calculate the trajectories of droplets within the respiratory tract.The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet,and bronchi,larynx,and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords,and among which,over 90%of droplets over 5μm released from vocal cords deposited at the larynx and pharynx-larynx junction.Generally,droplets’deposition fraction increased with their size,and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate.This threshold size for droplets released from the vocal folds was 10-20μm,while that for droplets released from the bronchi was 5-20μm under various airflow rates.Besides,successive syllables pronounced at low airflow rates promoted the escape of small droplets,but do not significantly affect the droplet threshold diameter.This study indicates that droplets larger than 20μm may entirely originate from the oral cavity,where viral loads are lower;it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.

A cost-effectiveness assessment of the operational parameters of central HVAC systems during pandemics

The present study develops a cost-effectiveness assessment model to analyze the performance of major operational parameters of central HVAC systems in terms of airborne transmission risk,energy consumption,and medical and social cost.A typical multi-zone building model with a central HVAC system is built numerically,and the effect of outdoor air(OA)ratio(from 30%to 100%)and filtration level(MERV 13,MERV 16,and HEPA)are assessed under the conditions of five climate zones in China.Compared with the baseline case with 30%OA and MERV 13 filtration,the airborne transmission risk in zones without infector is negligibly reduced with the increase in OA ratio and the upgrade of filtration level,owing to their slight modification on the equivalent ventilation rate of virus-free air.However,depending on climate zone,a 10%increase in OA ratio results in 12.5%-78.6%and 0.1%-8.6%increase in heating and cooling energy consumption,respectively,while an upgrade of filtration level to MERV 16 and HEPA results in an increase of 0.08%-0.2%and 1.4%-2.6%,respectively.Overall,when compared to the use of 100%OA ratio and HEPA filtration,the application of 30%or 40%OA ratio and MERV 13 filtration would save annually an energy and facility related cost of$29.4 billion in China,though giving an increase of approximately$0.1 billion on medical and social cost from the increased number of confirmed cases.This study provides basic method and information for the formulation of cost-effective operational strategies of HVAC systems coping with the airborne transmission,especially in resource-limited regions.

Can we migrate COVID-19 spreading risk?

It is well recognized that Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2)virus could be spread through touch and large droplets.However,we may have under-estimated the disease transmission by small droplets or aerosols that contain SARS-CoV-2 virus.Social distancing in public transport vehicles,such as airplanes,is not feasible.It is also not possible to wear masks in restaurant.This paper recommended wearing masks in airplanes and use partition screens in the middle of a table in a restaurant to reduce the infection caused by SARS-CoV-2 virus.Advanced ventilation systems,such as personalized ventilation and displacement ventilation,are strongly recommended for transport vehicles and buildings.

Control of exhaled SARS-CoV-2-laden aerosols in the interpersonal breathing microenvironment in a ventilated room with limited space air stability

The Coronavirus Disease 2019(COVID-19)highlights the importance of understanding and controlling the spread of the coronavirus between persons.We experimentally and numerically investigated an advanced engineering and environmental method on controlling the transmission of airborne SARS-CoV-2-laden aerosols in the breathing microenvironment between two persons during interactive breathing process by combining the limited space air stability and a ventilation method.Experiments were carried out in a full-scale ventilated room with different limited space air stability conditions,i.e.,stable condition,neutral condition and unstable condition.Two real humans were involved to conducted normal breathing process in the room and the exhaled carbon dioxide was used as the surrogate of infectious airborne SARS-CoV-2-laden aerosols from respiratory activities.A correspondent numerical model was established to visualize the temperature field and contaminated field in the test room.Results show that the performance of a ventilation system on removing infectious airborne SARS-CoV-2-laden aerosols from the interpersonal breathing microenvironment is dependent on the limited space air stability conditions.Appropriate ventilation method should be implemented based on an evaluation of the air condition.It is recommended that total volume ventilation methods are suitable for unstable and neutral conditions and local ventilation methods are preferable for stable conditions.This study provides an insight into the transmission of airborne SARS-CoV-2-laden aerosols between persons in ventilated rooms with different limited space air stability conditions.Useful guidance has been provided to cope with COVID-19 in limited spaces.