How to prevent second-hand smoke can a mask prevent second-hand smoke?

general dust masks and medical masks are useless. Including smog is useless. I recommend you to see the mask of 3m. Masks that can reach n9 or above can prevent second-hand smoke and smog. Medical masks sold by pharmacies for a few cents can prevent dust at most. A mask that can prevent second-hand smoke is basically the same as a gas mask. Good air tightness. 3m has several models with breathing valves, which are very good. Not too expensive. Twenty dollars for three packs. Take smog as an example, running outside every day. One can last four or five days. It's a good deal. If people near you smoke every day. Then advise each other. It's too bad to live on a mask.