"Acrylic board" for infection control actually has the opposite effect? Pointed out that ``air stays and ventilation is obstructed'' … Multiple infection control measures are required

Will the current measures against the new coronavirus infection not work? Acrylic panels and vinyl curtains, which are often used as partitions in offices and restaurants, have been pointed out to have the opposite effect, such as leaking viruses and blocking ventilation, depending on the situation.

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The number of new infections in Tokyo on the 5th was 1,853, falling below the same day of the previous week for the 14th consecutive day. While the number of infections continues to decline, a metropolitan government monitoring meeting pointed out that "the number of infected people in the workplace is at an extremely high level."

　According to a study published in July by the British Government's Emergency Scientific Advisory Group, partitions such as acrylic plates are effective for large particles emitted by vigorous coughing, etc., but the slow speed of exhaling during conversation etc. It was pointed out that it is difficult to prevent such small particles from mixing with the air in the room.

Kunio Yano, Special Advisor for Infectious Disease Control at Hamamatsu Medical Center, said, "The delta strain is highly contagious, and the amount of virus emitted from the mouth increases, so there is a risk of aerosol (particles floating in a mist) infection through conversation. Most of them are caused by droplets, so there's no need to think negatively about partitions in restaurants and the like, but they can't be completely prevented, and large ones can block the flow of air."

　A research team led by Project Associate Professor Yo Ishigaki (information engineering) at the University of Electro-Communications conducted a survey of office clusters (groups of infected people) that occurred in eastern Japan.

　The 180 square meter office was divided into 4 compartments with vinyl panels about 1.6 meters high, and there was about 80 centimeters of space near the ceiling. came out.

　The team used dry ice and smoke to reproduce the air flow at the actual site and in the laboratory. When only one entrance was opened for ventilation, the air remained in the section where many infected people were exposed.

　Mr. Ishigaki said, ``Small acrylic plates in restaurants and other places are only effective against direct droplets.Large partitions are also effective against droplets, but air stays and hinders ventilation. If there are more than one, it can be dangerous," he said.

　The concentration of carbon dioxide (CO2) due to dry ice gradually decreased from near the entrance, but after about 10 minutes the concentration had only decreased by 10%. On the other hand, with the window open, it decreased by more than 60% in 10 minutes, and with the window open and the ventilation fan added, it decreased by nearly 90% in 10 minutes.

　Mr. Ishigaki said, "If you can't open windows or turn on ventilation fans, you need to purify with an air purifier. There are holes in just one measure, so it's better to combine multiple measures such as masks and ventilation. Let's go," he advised.

　In some cases the window cannot be opened.

Mr. Yano said, "If it is not possible to ventilate the workplace, it is necessary to keep a distance of 1-2 meters between employees. There are many points where it is not known whether ventilation equipment is effective in eliminating viruses, so aerosols should be used. It's difficult to get it to zero, but we need to make efforts to dilute it."