Ventilation Requirements and Recommendations for Controlling SARS-CoV-2 and Variants Outbreaks in Indoor Gathering Places with Close Contact

Unexpected rapid infection involving SARS-CoV-2 variant Omicron known as the fifth wave of outbreak occurred since early January 2022 in Hong Kong. Almost 1.2 million citizens were infected in three months. Ventilation provisions in some gathering places with close contact such as restaurants were found to be lower than requirements, believed to be one of the main causes of transmission in these indoor spaces. At the end of the fifth outbreak in mid-May 2022, group infections were still found in several such gathering places including restaurants and pubs due to inadequate ventilation provisions. There are worries about triggering the sixth wave of outbreak. Key points related to ventilation requirements in such gathering places are discussed in this paper. Adequate ventilation of 6 air changes per hour minimum must be provided to avoid direct air transmission of virus. Indoor aerodynamics induced by ventilation system must be considered too. However, it is difficult to measure ventilation rate quickly and accurately. A control scheme on virus outbreaks is proposed on installing mechanical ventilation energy use meters and carbon dioxide sensors for checking ventilation provisions adequacy quickly.