Officials are warning of windblown ash and other pollutants from Los Angeles area fires and say air quality readers won't pick up on the ash pollutants.

Smoke exposure can especially pose a problem when the smoke comes from urban areas with more than just vegetation to burn, Dr. Lipi Roy said.

Particles from wildfire smoke can be much smaller than the width of a human hair. They are dangerous because they can be inhaled and travel deep into the lungs and enter the bloodstream, the EPA says. They can cause respiratory irritation and shortness of breath, and they can make conditions worse for people with asthma and heart disease.

Wildfires can expose people to harmful airborne compounds like ash and smoke. Research has shown that even months after a fire is out, people returning to

Dr. Lisa Patel, with the Stanford School of Medicine, details how you can protect yourself from the dangers of wildfire smoke in California and across the country.