Address: 2165 Highway V
              St. Charlews, MO 63301
County: Saint Charles  
Pollutant monitored: Ozone (O3)
Site coordinates
   * Latitude: 38.8994
   * Longitude: -90.44917
EPA site ID: 29-183-1004

Ozone (O3) Data*

The federal ozone season runs from March 1 through October 31.

As of 2015, the federal standard for ground-level ozone is 70 parts per billion. An area is in compliance if the design value
is at or below this standard. A design value for ozone incorporates data from three years. The department and EPA
calculate the design value by 1) ranking the daily eight-hour ozone values for three consecutive years;
2) extracting the fourth-highest value for each year; and 3) averaging the three figures.

Weekly summary of preliminary data from all ozone sites

Preliminary one-hour averages from the Orchard Farm site
   • "P" stands for primary monitor. "S" stands for secondary monitor.
   • Data from 10 days ago through current date
   • Central Standard Time
   • Concentrations of pollutant in parts per million (ppm)

Preliminary eight-hour forward-rolling averages from all ozone sites
   • Hourly data equal average of that hour and the following seven hours.
   • Data from 10 days ago through current date
   • Central Standard Time
   • Concentrations of ozone in parts per million (ppm)

Preliminary one-hour ozone averages from all sites

   • Data from 10 days ago through current date
   • Central Standard Time
   • Concentration of ozone in parts per million (ppm)

2016 exceedances of ozone standard

Graph of design values for ozone sites in St. Louis area, beginning in 2003

Additional information about ground-level ozone

*Technical issues can affect ability to deliver quality data.
Access a table of symbols indicating technical issues.

Related Links

Missouri's network of air monitoring sites

National standard for pollutants

Real-time views from cameras in Kansas City and St. Louis

Daily Air Quality Forecast (AirNow) shows how current readings
at air monitoring sites rate on the EPA's Air Quality Index.
Click on Missouri in the state box at the top of the home page
to access information.

EPA's Air Sensor Toolbox for Citizen Scientists