Welcome to the Wisconsin Department of Natural Resources Air Quality Monitoring Data site. 

General Information

The statewide monitoring network is spatially distributed to provide air quality information based on geographic coverage and population density. As required by the Clean Air Act, the U.S. EPA sets National Ambient Air Quality Standards (NAAQS) for criteria pollutants:

• Ozone (ground level)
• Particulate matter
• Sulfur dioxide
• Nitrogen oxides
• Carbon monoxide
• Lead

The DNR conducts ambient air monitoring in locations directed by federal requirements to measure concentrations of these criteria pollutants for comparison to the appropriate NAAQS. For more extensive information visit DNR's air monitoring webpage.

Data Validity

• Data presented on this website are displayed in real time. They have not been fully quality assured and are therefore subject to change.
• Data are quality assured within six months of collection.
• Reports may not follow all rounding/truncation conventions required for comparison to the regulatory NAAQS. For example, 8-hour average ozone concentrations on this website have been rounded rather than truncated, so the values listed may be one part per billion (ppb) higher than their regulatory values.

Time

• Data posted are the most recent available, but may appear to be older due to several factors:
  • Data are transmitted from the monitoring stations to the website where current AQI values are calculated. These steps take several minutes, which result in a lag between data collection and AQI reporting.
  • Data are always presented in Central Standard Time, so data will appear to be an hour behind during Daylight Savings Time.

Air Quality Index (AQI)

• Read more on the Air Quality Index Basics page.
• For more information on the federal particle pollution standard, review the EPA’s Final Updates to the Air Quality Index for Particulate Matter Fact Sheet and Common Questions document.

Parameter Specifications

• PM_2.5 – micrograms per cubic meter in local conditions
• PM₁₀ – micrograms per cubic meter corrected to standard conditions (25 °C, 1 atmosphere pressure)
• PM Coarse (particulate matter between 10 and 2.5 mm in size) – micrograms per cubic meter in local conditions
  • Not expected to match the difference between PM₁₀ and PM_2.5 in many cases because the PM₁₀ concentrations have been corrected to standard conditions
• Barometric Pressure – station conditions corrected to sea level