@luckytran You don't need to study filtration physics to understand this. People sometimes need to take off masks to hydrate, eat, take medicine, etc. Especially in workplaces and during travel. The only want to make that work is to minimize spreading of particles into the environment.
@幸运的是，你不需要学习过滤物理学就能理解这一点。人们有时需要摘下口罩来补充水分、进食、服药等，尤其是在工作场所和旅行期间。我们唯一想做的就是最大限度地减少颗粒物向环境中的扩散。