To identify potential countermeasures for coronavirus disease (COVID-19), we determined the air exchange rates in stationary and moving train cars under various conditions in July, August, and December 2020 in Japan. When the doors were closed, the air exchange rates in both stationary and moving trains increased with increasing area of window-opening (0.23–0.78/h at 0 m², windows closed to 2.1–10/h at 2.86 m², fully open). The air exchange rates were one order of magnitude higher when doors were open than when closed. With doors closed, the air exchange rates were higher when the centralized air conditioning (AC) and crossflow fan systems (fan) were on than when off. The air exchange rates in moving trains increased as train speed increased, from 10/h at 20 km/h to 42/h at 57 km/h. Air exchange rates did not differ significantly between empty cars and those filled with 230 mannequins representing commuters. The air exchange rates were lower during aboveground operation than during underground. Assuming that 30–300 passengers travel in a train car for 7–60 min and that the community infection rate is 0.0050–0.30%, we estimated that commuters’ infection risk on trains was reduced by 91–94% when all 12 windows were opened (to a height of 10 cm) and the AC/fan was on compared with that when windows were closed and the AC/fan was off.

为了确定冠状病毒病 (COVID-19) 的潜在对策，我们确定了 2020 年 7 月、8 月和 2020 年 12 月日本在各种条件下静止和移动的火车车厢的空气交换率。当车门关闭时，静止列车和移动列车的空气交换率均随着车窗开启面积的增加而增加（0 m ^{2时为 0.23-0.78/h，2.86 m 2}时车窗关闭至 2.1-10/h，完全打开）。门打开时的空气交换率比关闭时高一个数量级。在门关闭的情况下，中央空调 (AC) 和横流风扇系统 (风扇) 开启时的空气交换率高于关闭时的空气交换率。行驶中的列车中的空气交换率随着列车速度的增加而增加，从 20 公里/小时的 10 个/小时增加到 57 公里/小时的 42 个/小时。空车和装满 230 个代表通勤者的人体模型的汽车之间的空气交换率没有显着差异。地上操作期间的空气交换率低于地下操作期间。假设30-300名乘客乘坐火车7-60分钟，社区感染率为0.0050-0.30%，