I work in a lab where I sometimes have to wear chemical respirators (with a fitting session) and they still hurt my face and make it hard to breathe. When I had to spray insecticide on my garden I tried this. The flexible rubber design means you get a good seal (even with a small face) but it doesn't dig into your skin too much and you don't lose the seal when sweating or moving around. The stuff I was spaying smells pretty horrible, but I didn't notice till I took off the mask, so it is excluding well. Very adjustable and can still breathe fine .