We live in CA, and as usual we have the CA Wild Fires. This year is was especially close to home in Paradise. The air quality was awful, it was rated worse than anywhere in the world for a short amount of time. It was just miserable going outside. These masks for a lifesaver, we wore them anytime we went outside for about a week. It was amazing how much of a difference they made... and how filthy there were when we took them off.
I would highly recommend these.