The dirty air has sickened many who have taken shelter down the mountain from the Running Springs fire, CBS News correspondent Sandra Hughes reports.
"They are having some trouble breathing ... some even have tightness in the chest," said Dr. Margaret Beed of the San Bernadino County Department of Public Health.
When April Acosta was evacuated, she forgot to grab her asthma medicine. It's been three long days.
"You can't breathe," she said. "I started having panic attacks."
What's in smoke? Depending on what's burning, it could include:
Some of the chemical irritants and particulates can be so tiny that they're inhaled deep into the lungs.
"For a non-smoker, this is like smoking like half a pack or a pack [of cigarettes] a day," said Dr. Dee L'Archeveque of the Community Hospital of San Bernadino.
In the smokiest of areas, schools remain closed. And while the winds dying down is good news for firefighters on the frontlines, it isn't going to bring relief to people's lungs. Without those winds, the pollution isn't going anywhere.
So for now doctors are warning 'do not exercise outside,' and when you do have to go outside, and wear a mask.