From right, Daishiro Yamagiwa, minister in charge of economic revitalization, subcommittee chief Shigeru Omi, and Health, Labor and Welfare Minister Shigeyuki Goto are seen at a meeting of the Japanese government’s coronavirus response subcommittee in Tokyo’s Chiyoda Ward on July 14, 2022. (Mainichi/Kan Takeuchi)
TOKYO — The importance of ventilation to prevent aerosol transmissions was strongly emphasized by the Japanese government’s coronavirus response subcommittee amid the pandemic’s “seventh wave” in the country, where this time people will not be asked to curb their social and economic activities.
Aerosols are fine particles floating in the air and contain viruses exhaled from people infected with COVID-19. Even if you are more than 2 meters away from an infected person, you may still catch the virus by inhaling the floating aerosol. How can we effectively ventilate the room in the summer while lowering the room temperature with air conditioning?
Nobuaki Shimizu, a professor of infection control science at Aichi Prefectural University, says, “When a room is closed up because an air conditioner is on, aerosols containing viruses tend to accumulate and also drift into the air as humidity is lowered by the cooling effect.”
Shimizu considers inadequate ventilation to be one of the factors contributing to the recent rapid increase in the number of positive cases. The subcommittee’s recommendations also noted that COVID clusters that struck elderly care facilities, schools, and day care centers were often attributed to insufficient ventilation.
Shimizu emphasizes the importance of creating a strong air flow in places where people gather to prevent aerosols from accumulating, and to expel the air outside. Aerosols in exhaled air drift thickly near people, like cigarette smoke. The professor advises day care centers and other facilities to use “two-stage ventilation,” in which a small fan is placed on the floor to blow aerosols near children upward where there are no people, and then a stronger, larger stream of air passes through the room to blow the aerosols outside. He says, the system can also be applied at meetings and dinners by placing a small fan on a table.
For buildings without a ventilation system, the government subcommittee recommends opening windows. However, it’s difficult to open windows wide in the summer when considering the cooling effect of air conditioning. Thus, Shimizu advises that while using an air conditioner, decide on windows that serve as air inlets and outlets, and open them 10 to 15 centimeters at all times. Furthermore, if an air circulator or similar device is placed between the windows and air is blown into the direction of the exit, ventilation can be achieved without losing much cold air.
According to the subcommittee’s recommendation, if windows cannot be opened sufficiently to maintain room temperature, it is also effective to use air purifiers. In addition, if there is a ventilation fan, turn it on to exhaust air outside.
Meanwhile, unlike places where a large number of people gather, Shimizu says there is no need to be so nervous about ventilation in ordinary homes, and it is not necessary to take measures such as opening windows all the time.
(Japanese original by Mikako Shimogiri, Lifestyle and Medical News Department)