Orchard Farm Monitoring Station Image

Address: 2165 Highway V
              St. Charles, 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 federally mandated monitoring season for ground-level ozone runs from March 1 through October 31. Ground-level ozone forms when pollutants emitted by cars, factories, power plants and other sources react chemically in the presence of heat and sunlight. Ozone at ground level is a harmful air pollutant as opposed to ozone in the upper atmosphere, which protects us from ultraviolet light.

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
   • Eight-hour ozone design values
   • Four highest eight-hour ozone values from beginning of ozone season
   • Running list of sites with exceedances from beginning of season
   • Monthly number of exceedance
   • Map of Missouri's ozone monitoring sites
   • Daily maximum average eight-hour concentration for each site from beginning of season

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

Department's webpage about ground-level ozone
   • Description
   • Health effects
   • Tips to reduce ozone
   • 2008 and 2015 standards plus related documents

*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

Department's webpage about air quality
   • Air quality forecasts for St. Louis, Kansas City and Springfield during ozone season: March 1 through October 31
   • Tips for improving air quality
   • Tips for breathing better when air quality is forecasted to be unhealthy for sensitive groups (orange) or unhealthy (red)

Daily Air Quality Forecast (AirNow) gives air quality forecasts for cities nationwide.

EPA's Air Sensor Toolbox for Citizen Scientists

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