key: cord-0078035-z84xee0h authors: Xu, Chunwen; Yu, Chuck Wah Francis title: Prevention and control of COVID-19 transmission in the indoor environment date: 2022-05-08 journal: Indoor Built Environ DOI: 10.1177/1420326x221098883 sha: 1583cd42ba3bd3a21695ca3a51a9052e2ce3c255 doc_id: 78035 cord_uid: z84xee0h nan Chunwen Xu 1 The current global pandemic of the 2019 novel coronavirus disease COVID-19 has caused a serious global concern about human respiratory health. 1, 2 Particularly, the outbreak of the COVID-19 epidemic is found to be closely related to the transmission of infectious particles between persons in indoor environments, which highlights the importance of implementing strict and effective measures to prevent and control the transmission of infectious diseases. [3] [4] [5] Measures for COVID-19 control should be established based on a clear understanding of transmission mechanisms and a full consideration of the context of use. The objective of this special issue is to explore potential measures for effective disease control in indoor environments, including homes, public buildings, hospitals, vehicles, etc. and to clarify their underlying mechanisms for mitigating the risk of the disease transmission. This special issue covers original research and review studies, mainly including the following topics: · Mechanisms of the generation of infectious droplets from occupants' respiratory activities · Aerodynamic behaviours of the novel coronavirus and its potential for airborne transmission · Viability of SARS-CoV-2 in the indoor environment and its influencing factors · Epidemiological studies on COVID-19 indoor transmission pathways · Dispersion and propagation characteristics of exhaled droplets in the indoor environment · Intervention measures and their effect on prevention and control of the disease transmission in the indoor environment · Evaluation of the exposure and infection risk of airborne disease for occupants · Proper design and operation of Heating, Ventilation and Air Conditioning (HVAC) systems as a control measure to reduce airborne disease transmission · Disinfection and air cleaning methods and their effectiveness for indoor airborne infection control This special issue includes a total of 19 contributions from 7 different countries. The received papers underwent a rigid peer review procedure for publication in the Journal, Indoor and Built Environment. Papers included in this special issue have been carefully selected to present the recent new findings of research focusing on the above topics. There are three review papers included in this special issue. The paper by Nielsen and Xu summarized multiple airflow patterns affecting the airborne transmission route in the microenvironment between people and highlighted the importance of understanding the complex flow dynamics and interactions to prevent and control short-ranged airborne transmission. Ye et al. provided a systematic investigation of the Chinese HVAC guidelines for different occasions (e.g. office buildings, schools, hotels, hospitals, etc.) to cope with the COVID-19 transmission and compared them with guidelines from other countries or institutions. The possibility of transformation of the HVAC system between normal time and epidemic period and the novel HVAC system designs aiming at reducing indoor infection risk were also discussed. Yun et al. reviewed different methods for sampling and detecting the airborne virus including SARS-CoV-2 and they pointed out the lack of standardization for sampling and detection of the virus. Emission and dispersion of droplets from different respiratory activities like coughing, sneezing or breathing were studied by a number of authors in the following three papers. Pallares and Fabregat proposed a model to predict the shape and dimension of exhaled clouds containing droplets or droplet nuclei from coughing or sneezing. presented a method to determine the relative risk of airborne transmission that can be readily deployed with either modelled or monitored CO 2 data and occupancy levels within an indoor space. The interpersonal transmission of expiratory droplet nuclei in close proximity was measured by Fu et al. with two breathing thermal manikins and atomized particles as tracers. The size distribution of droplet nuclei and relative distances between occupants would significantly affect the intake fraction of the exposed occupant by inhalation. Chow and Chow proposed a two-stage quarantine scheme with quarantining people into units within blocks to control the spread of SARS-CoV-2 and to identify asymptomatic patients with a more targeted screening test. Ventilation is considered an effective way to prevent and control the airborne transmission of SARS-CoV-2 in the indoor environment. The effectiveness of using a vertical laminar airflow system in a hospital patient room and the negativepressure ventilation in isolation spaces in residential homes to prevent SARS-CoV-2 transmission were studied by Jeong et al. and Khan et al., respectively. Munuzuri et al. dealt with optimized natural ventilation times by incorporating local meteorological data with building parameters for the purpose of improving the epidemiological security of occupants. Additionally, a case study was conducted by Li et al. from Peking University in China to investigate the social organisation of makeshift hospital patients so as to reveal the social and emotional ramifications of such emergency spaces on people. As mentioned before, the goals of this special issue were to develop new knowledge of the transmission of COVID-19 and to effectively predict, prevent and control the infection risk of this disease. We hope the readers of the Indoor and Built Environment can help us to achieve these goals based on the papers included in this special issue. The 2019-nCoV epidemic control strategies and future challenges of building healthy smart cities Prediction and control of aerosol transmission of SARS-CoV-2 in ventilated context: from source to receptor HVAC systems for environmental control to minimize the COVID-19 infection Evaluation of indoor disinfection technologies for airborne disease control in hospital Transport and trajectory of cough-induced bimodal aerosol in an air-conditioned space All authors contributed equally in the preparation of this article. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.