Air Quality Monitoring

The Placer County Air Pollution Control District (District) operates an air quality monitoring network using a combination of equipment to provide current air quality information to help you make informed decisions to protect your health and the health of your family.

In Placer County, two pollutants are monitored – ozone and fine particulate matter (PM2.5) – at five stationary / permanent air monitoring sites. The monitoring stations operate 24-hours per day, seven days a week collecting both ozone and PM2.5 data.

The District also operates a temporary particulate monitor when needed and has deployed PurpleAir sensors in areas throughout the county for additional particulate monitoring.

You can view air monitoring data throughout California on CARB's Breathe Well website. Hourly data is listed in PST – Pacific Standard Time. Air quality data both for both ozone and PM2.5 from the five permanent monitoring stations in Placer County can be found by clicking the site name below. 

AuburnColfaxLincolnRosevilleTahoe City


PurpleAir sensor information for sites specifically in Placer County are listed below:

AltaAuburnForesthillLoomisOlympic ValleyRocklinSheridan


Ambient Air Quality Standards

The U.S. Environmental Protection Agency (U.S. EPA) and the California Air Resources Board (CARB) have both set health-based ambient air quality standards for pollutants. The current federal and state standards can be found here.

The data collected from the monitoring sites is used for comparison to the National and State Ambient Air Monitoring Standards to determine if the standards are met. Currently, Placer County does not meet the federal and state ambient air quality standards for two pollutants – ozone and PM2.5.

Ground-Level Ozone

Ground-level ozone is formed when volatile organic compounds (VOCs) and oxides of nitrogen (NOx) react with the sun's ultraviolet rays. The primary source of VOCs and NOx is mobile sources, including cars, trucks, buses, construction equipment and agricultural equipment.

Ground-level ozone reaches its highest level during the afternoon and early evening hours. High levels occur most often during the summer months. Ozone is a strong irritant that can cause constriction of the airways, forcing the respiratory system to work harder to provide oxygen.

Particulate Matter (PM)

Particulate Matter is a complex mixture that may contain soot, smoke, metals, nitrates, sulfates, dust, water, and tire rubber. It can be directly emitted, as in smoke from a fire, or it can form in the atmosphere from reactions of gases such as nitrogen oxides.

The size of particles is directly linked to their potential for causing health problems. Small particles (known as PM2.5 or fine particulate matter) pose the greatest problems because they bypass the body’s natural defenses and can get deep into your lungs and potentially your bloodstream. Exposure to such particles can affect both your lungs and your heart.

To understand more easily what the air quality data measurements for both these pollutants mean, the data is converted into the U.S. EPA's user-friendly Air Quality Index (AQI).

What is the AQI and What Does it Mean?

The Air Quality Index, or AQI, is a user-friendly health-based scale created by the U.S. EPA that uses color-coding and numbers to help one quickly understand air pollution levels. Each AQI color range has a descriptor with a public health advisory. The higher the AQI value, the greater the level of pollution and corresponding health concern. 

When the AQI is in the green / "good" range (0 - 50), air quality poses little to no risk. However, as the AQI moves from the yellow / "moderate" range into the orange / "unhealthy for sensitive groups" range (100-150), sensitive groups such as children, elderly, pregnant people, and those with existing heart and lung conditions may begin to experience health effects. With higher AQI levels – red / "unhealthy", purple / "very unhealthy", and maroon / "hazardous"  more of the population is expected to experience health effects. Those with greater sensitivity may also notice adverse health effects sooner. 

More information on   Air Quality and Health can be found here.

Additional Air Quality Conditions and Forecasts

To learn more about air monitors, sensors, and understanding and using air monitoring and sensor data, check out this fact sheet on  How to Interpret Online Monitoring Information. The websites below can be used to view the conditions and forecast in your area of interest.

  • Sacramento Area Regional Spare the Air Check daily air quality current conditions and forecasts for the Sacramento area. This information is provided using the AQI for communities in the region. Air quality conditions and forecasts can be heard on radio and TV weather reports, newspapers, and through social media. Sign up for air quality notifications with   Air Alerts.
  • U.S. EPA's AirNow Get the air quality in your local area or your area of interest. The current air quality and forecast is presented using the AQI on an interactive map that presents air quality information for the entire country from permanent air monitoring sites. 
  • U.S. EPA and USFS's Fire and Smoke Map – This interactive map provides air quality and smoke information to the public. It shows data not only from stationary / permanent and portable monitors but also includes PurpleAir low-cost sensor info. With the increased use of PurpleAir sensors, it is easy to see widespread smoke impacts in an area.

Air Quality Data

To view the data collected from each of the five monitoring stations, click on the links below.

  • CARB's Air Quality and Meteorological Information System (AQMIS)  CARB's database collects preliminary monitoring data from all stationary / permanent monitors in California. This webpage provides options to search air quality data based on the types of pollutants, area, types of measurements, data, and time. It also provides a customizable visual display of air quality or meteorological data for each site on a Google map.
  • CARB's Air Quality Data Statistics (iADAM)  Select and view air quality data for various pollutants throughout the State.