SonomaCountyRecovers: Official recovery information for Sonoma County fires

Air Quality in Sonoma County

For answers to frequently asked questions including “What precautions should residents take to prevent ash from coming into my home?” and “What can I do to ensure air quality in my home is safe?” click here.

There are three categories of air quality data that will be available:

  • Routinely collected air quality data from fixed monitors from the Bay Area Air Quality Management District (BAAQMD) and Northern Sonoma County Air Pollution Control District (NSCAPCD).
  • Supplemental air quality data from recently placed mobile monitors. This includes California Air Resources Board monitors placed at Sonoma County schools located near debris sites.
  • Debris site monitoring conducted by US Army Corps of Engineers.

How do we measure air quality?

One of the most common ways to measure air quality is by measuring particulate matter, or PM. PM refers to extremely small particles in the air that are detrimental to your health. PM2.5, also called “fine particulates,” consists of particles with diameters ≤ 2.5 microns. PM10 refers to “coarse particles” that have a diameter ≤ 10 microns. To learn more about PM, click here.

Air Quality Monitoring Data

Weather conditions and winds change dramatically during the winter months in the Bay Area. Frequently cool windless days will occur and an inversion layer sets in, a phenomenon when cooler air sinks and warm air aloft traps the air in our region. This causes air pollutants that we emit every day from driving, farming, industrial activities, and burning wood in fireplaces to build up and become trapped in the air.

Periodically, the Bay Area Air Quality Management District (BAAQMD) forecast higher particulate matter concentrations in the North Bay. This is often due to cooler temperatures in the North and the inland valleys and often trapped wood smoke pollution.

The winter weather pattern will continue intermittently throughout in Napa, Sonoma, and Marin counties. By late February to early March, this pattern will switch to a spring weather pattern allowing for more air disbursement.

For Sebastopol: To find information on the most recent PM2.5 air quality data, please click here. 

For Cloverdale, Healdsburg, and Guerneville: To find information on the most recent Air Quality Index (AQI) by the Northern Sonoma County Air Pollution Control District, please click here.

Five-day forecast: If you’d like to see the current spare the air status and five-day forecast, please click here.

Click on the forecast to see what the map predictions will be.

The Bay Area Air Quality Management District developed this legend to help you understand the PM2.5 data. As established by the U.S. Environmental Protection Agency (EPA), the Air Quality Index for PM2.5 is based on 24-hour concentrations, so hourly readings are only estimates.

Air Quality Index Levels of Health Concern



0 to 50


51 to 100

Unhealthy for Sensitive Groups

101 to 150


151 to 200

Very Unhealthy

201 to 300


301 to 500


During northern California’s wildfire season, the Bay Area Air Quality Management District monitors general air quality in the Bay Area and will issue a health advisory if wildfire smoke appears to be causing elevated levels of particulate pollution in the region.

The Sonoma County Department of Health Services receives community area monitoring data through US Army Corps of Engineers (USACE). The USACE is one of several agencies in Sonoma County conducting air monitoring to ensure the safety of the community. The PM 10 Average Concentration readings, in general, were below the target criteria indicating no reportable risk based on particulates as a result of these readings.

The USACE is also overseeing area monitoring as part of debris management and clean-up.

As of December 1, PM 10 Average Concentrations are being monitored during debris removal. PM10 includes inhalable particles with diameters that are generally 10 micrometers and smaller. PM10 is a more conservative approach to air monitoring, which captures everything below 10 micrometers, including PM2.5.

PM 10 Average Concentration readings, in general, were below the target criteria indicating no reportable risk based on particulates as a result of these readings. On 12/14 and 12/15 PM targets were exceeded at the monitoring locations. These exceedances were evaluated and it was determined that they were due to increased vehicle traffic in the area. There were no exceedances for the offsite, downwind locations or nearest sensitive receptor. Additionally, maximum concentrations were all below targets and the maximum 3-hour averaged did not exceed action levels. Dust control measures in the form of watering and street cleaning were increased. Following these activities, PM10 levels at monitoring sites were below target levels.

Updated as 1.16.18

See Fire Debris Removal Air and Area Monitoring tracking tables here Dec 1-18 and Dec 19- Jan 8.

*This website is actively being developed and updated with additional information. Information is subject to change.


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