Air Quality & Smoke Readiness

Smoke exposure from wildfires is an increasingly common public health hazard to communities throughout California. Knowing where to find accurate information and being prepared to act when smoke is in the air can help you protect yourself and your family. This factsheet provides background on the health impacts of smoke and an introduction to preparing yourself during smoke events.

What is Smoke?

Smoke is made up of a mixture of chemical compounds, including carbon dioxide, water vapor, and particles. Particulate matter (PM) is a primary pollutant of public health concern from short- and long-term smoke exposure. Particulate matter is grouped into two size classes: PM₁₀ (inhalable particles <10 microns) and PM_2.5 (fine particles < 2.5 microns). While smoke particles range in size, studies show that 90% of smoke particles from wildland fires fall into the PM₁₀ category and about 90% of those particles are within the PM_2.5 size range.

Health Effects of PM_2.5 Exposure

Fine particulate matter (PM_2.5) can penetrate deep into a person’s lungs causing inflammation, respiratory tract irritation, and other respiratory and cardiovascular impacts. The level and duration of smoke exposure, age, sensitivity, and other factors determine whether someone experiences adverse health effects from smoke. While most healthy adults and children may not experience long-term effects from smoke exposure, the following populations may be more vulnerable to the health impacts of smoke: children with developing lungs, children and adults with underlying pulmonary and cardiovascular diseases (e.g., asthma and COPD), outdoor workers, unhoused individuals, socioeconomically disadvantaged persons, and pregnant people. These groups should take greater precautions and be aware of the potential effect of pollutants on their health during wildfire events.

Understanding Air Quality Index (AQI)

The Air Quality Index (AQI) was created by the US Environmental Protection Agency to report air quality data in simple, understandable metrics. The AQI ranges from 0 to 500 with the higher numbers representing increasing levels of air pollution with greater public health concerns. The AQI is divided into six color-coded categories for quickly identifying air quality conditions.

Strategies for Reducing Smoke Exposure

Differences Between Prescribed Fire and Wildfire Smoke

The use of prescribed burns in strategic locations will help prevent wildfires from having extreme behavior, resulting in less smoke if a wildfire occurs in the treated area. While prescribed fire smoke can impact local air quality, prescribed fires are key to reducing long-term wildfire smoke exposure to communities. Prescribed fires typically produce less smoke than wildfires because they are planned events. Prescribed fires are only authorized during favorable weather conditions making them less likely to worsen overall air quality. Managers consider weather conditions so prescribed fires will be less intense and slower moving than wildfires and smoke will lift and disperse. Smoke from prescribed fires is also often less toxic than wildfire smoke because only vegetation is burned.