According to the "Views on Countermeasures for Coronavirus" (published on March 9 and 19, 2020) of the Council of Experts on Countermeasures for Coronavirus, the common condition that have been identified so far for mass infection are

(1) poorly ventilated enclosed spaces

(2) a large number of people were in close proximity

(3) conversations and vocalizations took place at close range (within reach of each other)

Although it is not considered to be transmitted via air, the possibility of micro-droplet infection has also been pointed out. Dusty indoor conditions can also put a strain on the throat and bronchial tubes, increasing the risk of infection.

• Ventilation frequency (the number of times all the air in the room is replaced by the outside air) at least twice per hour (at least once every 30 minutes, for a few minutes or so, with the windows fully open).

• Open at least two windows instead of just opening a window to allow air to flow

• If there is only one window, open the door.

• Can be used with a ventilation fan.

• Ventilate frequently rather than occasionally for a long time.

• It is important to "do it as much as you can without strain"

The Ministry of Health, Labor, and Welfare (MHLW) says that even in buildings without windows, reach the standard for the recommended ventilation for the virus if the Building Sanitation Law standards are met.

If you are a tenant in such a building, one of the things you can do now may be to check with the building owner or the building management company to make sure that the standards are met.