These are great masks 3M is the best brand but I do have a sensitized nervous system. It's very hard to explain. But things in the air hurt my nerves very bad. So I have to wear these to drive. And to walk into stores, because cigarette smoke and car exhaust fumes hurt me. Now I buy like a bunch of these, because they are not all perfect seals. It's impossible to find a perfect seal mask for someone like me. I'd say one out of every 7 mask are having a good seal. Where the others don't. I can't tell you exactly how bad the other ones are. But to me, it's extreme, it could just be a tiny bit that still seeped through compared to a lot. It's I don't know how to explain. I don't think you can ever find a perfect seal mask. They're very rare, even with brand new best filters out there. You're still gonna be breathing some stuff in. But I'll try on different masks in the same filters. In some mask are terrible. In some mask are great