So I work in a small, stuffy room and even when it was snowing out, I liked to have the window open for fresh air. But now that it's getting warmer, people are going outside and smoking and it's coming in here.

I want fresh air and I want the smoke filtered out before I breath it in. Is there something that I can buy that does it?

I can put fans in the window facing out..but then it doesn't seem like there is fresh/clean air in here.