There are 12 monitoring stations in central Indiana that measure for ground-level ozone. In addition to three Marion County sites, ground-level ozone is monitored in Noblesville in Hamilton County, Fortville in Hancock County, Avon in Hendricks County, Whitestown in Boone County, Monrovia in Morgan County, Trafalgar in Johnson County, Plummer in Greene County, Brownstown in Jackson County, and Fairland in Shelby County.
An ozone analyzer is a particularly sophisticated piece of equipment that can detect the presence of one molecule of ozone per a billion parts of air. Because ozone analyzers are extremely sensitive and complex, they must be placed inside temperature-controlled environments. Various federal and state site requirements must be followed to ensure proper monitoring.
The ozone analyzer samples ambient air through a probe located 9 to 45 feet above ground level and at least three feet away, vertically and horizontally, from any supporting structure. The probe is also located at least 60 feet from the drip line of trees because the effect of trees on ozone is greater than for other pollutants. An ozone site is generally a distance from major roadways to minimize the interference of vehicular traffic.
For current data on ground-level ozone levels, visit
The table below shows the 4th highest eight-hour average at each of the ozone monitoring sites for 2002, 2003, 2004 and 2005, which provides some insight into ground-level ozone trends in central Indiana.
