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.

Numerical study on the integrated effects of supplied air velocity and exhaust velocity on particles removal for industrial buildings

Due to production particularity in industrial buildings,high concentrations of particulate matter are always im-portant environmental issues.Long-term exposure to such hazardous environment may lead to respiratory and cardiovascular diseases.Mechanical ventilation plays a vital role in reducing indoor particulate matter concen-trations.However,the current industrial ventilation generally has the disadvantage of low ventilation efficiency and high energy consumption.In this study,we proposed a ventilation design by integrating supply and exhaust ventilation(i.e.,SEV),and further investigated the effects of combined velocities on both indoor particles re-moval and energy efficiency.Computational Fluid Dynamics(CFD)coupled with Discrete Phase Model(DPM)was employed.The RNG k-𝜀model was adopted to simulate airflow field.Lagrangian method was used to trace particles’dispersion processes.A series of cases were conducted under ventilated conditions with combinations of different supplied velocities of 0.75,1.12,1.50 and 1.87 m/s,and exhausted velocities of 0,0.28 and 0.56 m/s.Temperature effects were not considered in this work.The quantification of combined effects of supply velocity and exhaust velocity were investigated in terms of particle removal efficiency as well as energy saving.Results showed that combined effects of supply velocity and exhaust velocity can improve the ventilation efficiency by 20%-40%compared to the conventional supply ventilation without exhaust velocity.Moreover,the reasonable design of integrated velocities will save up to 70%energy while keeping the same ventilation efficiency of SEV.These findings will be of great importance for energy-efficient design for industrial ventilation systems.

Impact of ionizers on prevention of airborne infection in classroom

Infectious diseases(e.g.,coronavirus disease 2019)dramatically impact human life,economy and social development.Exploring the low-cost and energy-saving approaches is essential in removing infectious virus particles from indoors,such as in classrooms.The application of air purification devices,such as negative ion generators(ionizers),gains popularity because of the favorable removal capacity for particles and the low operation cost.However,small and portable ionizers have potential disadvantages in the removal efficiency owing to the limited horizontal diffusion of negative ions.This study aims to investigate the layout strategy(number and location)of ionizers based on the energy-efficient natural ventilation in the classroom to improve removal efficiency(negative ions to particles)and decrease infection risk.Three infected students were considered in the classroom.The simulations of negative ion and particle concentrations were performed and validated by the experiment.Results showed that as the number of ionizers was 4 and 5,the removal performance was largely improved by combining ionizer with natural ventilation.Compared with the scenario without an ionizer,the scenario with 5 ionizers largely increased the average removal efficiency from around 20%to 85%and decreased the average infection risk by 23%.The setup with 5 ionizers placed upstream of the classroom was determined as the optimal layout strategy,particularly when the location and number of the infected students were unknown.This work can provide a guideline for applying ionizers to public buildings when natural ventilation is used.

Low-carbon design towards sustainable city development:Integrating glass space with natural greenery

The rapid urban development has caused serious problems such as high energy consumption and carbon emissions,especially under the context of climate change.Buildings are particularly energy-intensive,generating about one third of global energyrelated carbon emissions.Compared with active solutions(like mechanical systems),passive solutions offer the potential to balance energy consumption,thermal comfort,and ecological benefits.One potential solution is the integration of green glass space(GGS)into passive building design.GGS is a transitional building space with glass curtain walls that exhibit excellent insulation performance during winter.However,GGS is susceptible to overheating during summer,which limits its applicability.Therefore,this work proposes a strategy of integrating vertical greenery into GGS,leveraging the nature-based solution of greenery(i.e.,flourishes in summer and withers in winter)to address this seasonal challenge of GGS.The results demonstrated that the strategic application of vertical greenery can effectively mitigate the overheating in GGS and improve comprehensive benefits.By using full coverage of vertical greenery in a linear layout,the air temperature of GGS and cooling energy consumption were largely reduced by 8.02℃and 12.2%,respectively,while the carbon abatement was enhanced by up to 101.11 tons.Based on a comprehensive evaluation of energy,economy,and environmental benefits,it is recommended to use a greenery configuration with 50%coverage in a vertical linear layout for GGS.The integration of greenery into building design can mitigate adverse environmental impacts,reduce energy consumption,and contribute to the sustainable development of low-carbon cities.

室内空气污染造成的疾病负担及为什么我们要了解它

Ask a scientist from basically any area of science what they think about the immense scientific complexity of indoor air and its impacts,and they seem perplexed.Complexity of black holes—yes,complexity of the human genome—yes,but of indoor air?To scientists who investigate indoor air it is incomprehensible that this area of science attracts so little interest from the broader scientific community,the public,and frankly,anyone.

Urban heat mitigation by green and blue infrastructure:Drivers,effectiveness,and future needs

The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change.Yet,the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure(GBGI),such as parks,wetlands,and engineered greening,which have the potential to effectively reduce summer air temperatures.Despite many reviews,the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear.This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits,identifies knowledge gaps,and proposes recommendations for their implementation to maximize their benefits.After screening 27,486 papers,202 were reviewed,based on 51 GBGI types categorized under 10 main divisions.Certain GBGI(green walls,parks,street trees)have been well researched for their urban cooling capabilities.However,several other GBGI have received negligible(zoological garden,golf course,estuary)or minimal(private garden,allotment)attention.The most efficient air cooling was observed in botanical gardens(5.0±3.5℃),wetlands(4.9±3.2℃),green walls(4.1±4.2℃),street trees(3.8±3.1℃),and vegetated balconies(3.8±2.7℃).Under changing climate conditions(2070–2100)with consideration of RCP8.5,there is a shift in climate subtypes,either within the same climate zone(e.g.,Dfa to Dfb and Cfb to Cfa)or across other climate zones(e.g.,Dfb[continental warm-summer humid]to BSk[dry,cold semi-arid]and Cwa[temperate]to Am[tropical]).These shifts may result in lower efficiency for the current GBGI in the future.Given the importance of multiple services,it is crucial to balance their functionality,cooling performance,and other related co-benefits when planning for the future GBGI.This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating,filling research gaps,and promoting community resilience.

Fast prediction for multi-parameters(concentration,temperature and humidity)of indoor environment towards the online control of HVAC system

Heating,ventilation and air conditioning(HVAC)systems are the most energy-consuming building implements for the improvement of indoor environmental quality(IEQ).We have developed the optimal control strategies for HVAC system to respectively achieve the optimal selections of ventilation rate and supplied air temperature with consideration of energy conservation,through the fast prediction methods by using low-dimensional linear ventilation model(LLVM)based artificial neural network(ANN)and low-dimensional linear temperature model(LLTM)based contribution ratio of indoor climate(CRI_((T))).To be continued for integrated control of multi-parameters,we further developed the fast prediction model for indoor humidity by using low-dimensional linear humidity model(LLHM)and contribution ratio of indoor humidity(CRI_((H))),and thermal sensation index(TS)for assessment.CFD was used to construct the prediction database for CO_(2),temperature and humidity.Low-dimensional linear models(LLM),including LLVM,LLTM and LLHM,were adopted to expand database for the sake of data storage reduction.Then,coupling with ANN,CRI_((T)) and CRI_((H)), the distributions of indoor CO_(2) concentration,temperature,and humidity were rapidly predicted on the basis of LLVM-based ANN,LLTM-based CRIm and LLHM-based CRM respectively.Finally,according to the self-defined indices(i.e.,E_(V),E_(T),E_(H)),the optimal balancing between IEQ(indicated by CO_(2) concentration,PMV and TS)and energy consumption(indicated by ventilation rate,supplied air temperature and humidity)were synthetically evaluated.The total HVAC energy consumption could be reduced by 35%on the strength of current control strategies.This work can further contribute to development of the intelligent online control for HVAC systems.

面向人因工程学的公共建筑空气环境安全运维与控制

公共建筑空间人员密集、人流量大,空气污染种类多并呈现非均匀动态的分布特性,给新冠肺炎疫情常态化空气安全保障带来了巨大挑战.采用过量送风不仅可能造成较大能源浪费,同时也可能导致交叉污染.从人因工程学的核心理念和基本方法出发,围绕室内空气污染水平(特别是人员散发的飞沫污染物)这一重要人因环境变量,发展了一套建筑空气环境安全运维控制系统.该系统基于室内空气污染和人员流动的动态监测,由快速预测模型以及计算机视觉处理得到室内污染与人员的非均匀动态分布,进一步通过环境控制决策系统输出最优通风参数设定,实现通风智能化调控;同时,在通风环境营造基础上构建空气净化消杀系统,对空气环境安全运维形成有力的辅助保障.最后,通过实际案例(某国际会议中心前厅)详细展示了该系统的工作流程和设计效果.设计结果显示,实施智能化通风可将人员感染风险降低至4%以内,其通风节能率可达44.9%;负氧离子的空间可达性较好且空间消杀率计算值超过99%,可进一步降低感染风险.