I have breathing problems as well, have found the following helps:
1. Go to hardware store and get a face mask (one of those that conforms to your face, with two elastics). Pretty cheap, I got a pack of 5 from Lowe's on Jamboree for $3 or so. Wear it outside for sure, or indoors if needed as well. Makes the air you breathe in a lot moister, and filters out a lot of the smoke particles (ie. these are the masks people wear when they go do sanding or whatever, so that makes sense).
2. Try and get the humidity up. Can just put some water in the bathtubs if don't have a humidifier.
3. Drink lots of water
Or, if you just can't take it anymore (I couldn't on Friday) - drive to a museum where they keep the expensive stuff (ex. California Natural History museum, Los Angeles Art Museum). Natural History museum was great on Friday - perfect air inside there - no trace of smoke, perfect humidity. Those are the places that have the premium air filtering to protect all the valuable stuff inside.