If you still feel the need to cover up your nose and mouth, you can get some protection from a basic surgical mask. But only some. Unlike an N95 mask, a surgical mask has a looser seal against the face so there’s room for germs to get in. Aaron E. Glatt, chair of medicine at Mount Sinai South Nassau and a spokesperson for the Infectious Diseases Society of America, says a surgical mask works as a physical barrier, but “it’s not clear how much benefit you’re getting because you also breathe in the air around the sides of the mask, where there is potentially infectious material as well.” And Javaid cautions that you’ll only reap the benefits if you use it properly: washing your hands after taking it off, not touching the outside of the mask, only using each mask once, and replacing it if it gets wet. If you’re still worried about getting sick, you’re better off following common-sense advice on avoiding illness. “Everybody wants masks,” says Glatt, but he instead stresses basic good hygiene: “Stay home [if you’re sick], don’t infect anybody, wash your hands appropriately, and get vaccinated.” In fact, all three doctors we consulted say you’re much more likely to catch the flu than the coronavirus, so definitely get vaccinated if you haven’t already. We have more advice from doctors on avoiding colds here, but below are the two most important items you can add to your cart, whether you’re trying to avoid the coronavirus, the flu, or an everyday cold.
+ from internet: A surgical mask, also known as a procedure mask medical mask or simply as a face mask, is intended to be worn by health professionals during surgery and during nursing to catch the bacteria shed in liquid droplets and aerosols from the wearer's mouth and nose. They are not designed to protect the wearer from inhaling airborne bacteria or virus particles and are less effective than respirators, such as N95 or FFP masks, which provide better protection due to their material, shape and tight seal. 医用口罩不是用来保护带口罩的人吸入病菌，而是用来防止呼出病菌的。
看你打算怎么用，贴身照顾新冠病人不够的，其他低危环境用来阻止手摸脸可以。。。
外科医生动手术的时候要带更多是避免细菌感染病人吧
你意思是，医生的细菌比病人多，所以要保护病人不被医生感染？
有种说法是外科手术的口罩是单向的，但除了牛妈，我还没从其他途径验证。
If you still feel the need to cover up your nose and mouth, you can get some protection from a basic surgical mask. But only some. Unlike an N95 mask, a surgical mask has a looser seal against the face so there’s room for germs to get in. Aaron E. Glatt, chair of medicine at Mount Sinai South Nassau and a spokesperson for the Infectious Diseases Society of America, says a surgical mask works as a physical barrier, but “it’s not clear how much benefit you’re getting because you also breathe in the air around the sides of the mask, where there is potentially infectious material as well.” And Javaid cautions that you’ll only reap the benefits if you use it properly: washing your hands after taking it off, not touching the outside of the mask, only using each mask once, and replacing it if it gets wet. If you’re still worried about getting sick, you’re better off following common-sense advice on avoiding illness. “Everybody wants masks,” says Glatt, but he instead stresses basic good hygiene: “Stay home [if you’re sick], don’t infect anybody, wash your hands appropriately, and get vaccinated.” In fact, all three doctors we consulted say you’re much more likely to catch the flu than the coronavirus, so definitely get vaccinated if you haven’t already. We have more advice from doctors on avoiding colds here, but below are the two most important items you can add to your cart, whether you’re trying to avoid the coronavirus, the flu, or an everyday cold.
如果你的手伸进口罩里擦鼻子。那没有用。
手术室要求无菌环境啊，不戴口罩怎么保证无菌环境
想起个事儿。。。医生手术的时候出汗，护士没来得及擦，眼睁睁看着掉进。。。
双向保护。
1是防止医生呼出的气体或和助理手术师交谈时的唾液碰到病人的切口造成感染。
2是防止开刀时病人的血液，组织液飞溅到医生的脸部造成感染。
病毒直径小于125nm 口罩孔径一般大于300nm 所以戴口罩作用不大
美国空气相对比较好 微小颗粒少
口径小于300nm的生化口罩 呼吸比较费力
就是，肺病居然不需要戴口罩，真是奇葩的guidance
+ from internet:
A surgical mask, also known as a procedure mask medical mask or simply as a face mask, is intended to be worn by health professionals during surgery and during nursing to catch the bacteria shed in liquid droplets and aerosols from the wearer's mouth and nose. They are not designed to protect the wearer from inhaling airborne bacteria or virus particles and are less effective than respirators, such as N95 or FFP masks, which provide better protection due to their material, shape and tight seal.
医用口罩不是用来保护带口罩的人吸入病菌，而是用来防止呼出病菌的。
为了防止飞沫传染，他还设计发明了一种双层纱布口罩，用于隔离病患，后来这种口罩被称为——“伍氏口罩”。这种口罩的制作方式很简单，采用药店出售的普通外科纱布，约9寸宽，剪成3尺长，每条顺长折成双层，中间放置一块长4寸、宽6寸、厚半寸的棉花，再将纱布的每端剪成两条，每条长15寸，使之成为两层状的纱布绷带，用时以中间有棉花处掩遮口鼻，两端的上尾，须经耳朵上方缚结于脑后，两端的下尾也如此，只是须经过耳朵下方。
如此自制的口罩，简单易戴，价格低廉，每个只需国币二分半，伍连德调动了大量人力物力，确保口罩源源不断地供应给市民，并且很快被民众接受。
在1911年召开的“万国鼠疫研究会”上，这种方便又实用的口罩，受到了各国医学专家的赞赏，“伍连德发明之面具，样式简单，制造费轻，但服之效力，亦颇佳善。”
110年以后，CDC和绝大多数美国医护认为，面对新冠这种烈性大流行呼吸道传染病，戴口罩没用甚至有反效果，自己坚持裸奔并洗脑民众，果然是宇宙第一大国的水准和胆识。
就是，没用的话，FBI买口罩干嘛？吃饱了撑的？
SARS 时候，口罩不够用，中国的医护人员也自制纱布口罩来着
给医护人以及病人有用，给你没用！想带先去感染个病毒啊！