The transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs via contact with contaminated surfaces and inhalation of large airborne droplets and aerosols. As growing evidence of airborne SARS-CoV-2 transmission has been reported worldwide, ventilation is an effective method of reducing the infection probability of SARS-CoV-2. This leads to such questions as “What is a sufficient ventilation rate for avoiding the risk of COVID-19 infection?” Therefore, this study evaluates the critical ventilation rates according to room size and exposure time when a susceptible person is in the same room as an infector. The analytical results were based on data obtained from 70 confirmed COVID-19 cases transmitted in confined spaces without an operational ventilation system. The results reveal that even with active ventilation (20 h⁻¹ air exchange rate), the critical exposure time for a susceptible person with a COVID-19 infector in a small space of 20 m³ is less than 1 h. For other cases (different space sizes), the estimated air exchange rates for avoiding the risk of infection are generally higher than various requirements for good indoor air quality. The findings of this study will provide guidelines for determining sufficient ventilation rates to protect against the highly contagious COVID-19.

严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 的传播是通过接触受污染的表面和吸入空气中的大飞沫和气溶胶而发生的。随着全球报道越来越多的空气传播 SARS-CoV-2 传播的证据，通风是降低 SARS-CoV-2 感染概率的有效方法。这导致了诸如“避免感染 COVID-19 风险的足够通风率是多少？”之类的问题。因此，本研究根据房间大小和易感人群与感染者在同一个房间时的暴露时间来评估临界通风率。分析结果基于从 70 例确诊的 COVID-19 病例中获得的数据，这些病例在没有运行通风系统的密闭空间内传播。结果表明，即使有主动通气（20 h⁻¹空气交换率），感染 COVID-19 的易感人群在 20 m ³的小空间内的临界暴露时间小于 1 小时。对于其他情况（不同的空间大小），用于避免感染风险的估计空气交换率通常高于对良好室内空气质量的各种要求。这项研究的结果将为确定足够的通风率以防止高度传染性的 COVID-19 提供指导。