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current air quality in Wisconsin.
previous days air quality data reports.
for current air quality advisories.
A clear winter day at DNR's Mayville air monitoring site

Platform with monitoring equipment at the Horicon monitoring site.

Contact information

Statewide monitoring program:
Katie Praedel
Data quality assurance:
Jason Treutel

Air quality monitoring

Wisconsin's ambient air quality monitoring network provides timely access to air quality information, supports planning for air quality improvements and ensures program accountability. The network focuses on EPA's list of the most serious health-related air pollutants: ozone, particle pollution, sulfur dioxide, nitrogen dioxide and carbon monoxide. Using continuous monitoring data, DNR quickly informs the public when air pollution reaches unhealthy levels. Based on these notices, people may adjust their daily activities to minimize adverse health effects.

To see how Wisconsin's air quality compares with the rest of the nation, check out U.S. EPA AIRNOW [exit DNR].

Network review

Network review

Annual review

The DNR periodically reviews its air monitoring network and provides an opportunity for public input on monitoring locations and pollutants to be monitored.

Five-year network assessment

Every five years, states are required to perform a more extensive assessment of its network to ensure the best possible use of available resources to meet policy, regulatory and technical needs. Wisconsin DNR staff cooperated with representatives from the States of Illinois, Indiana, Michigan, Minnesota and Ohio, local agencies, as well as U.S. EPA and the Lake Michigan Air Directors Consortium to develop a 5-Year Network Assessment [exit DNR] that provides a broader, more comprehensive evaluation of the monitoring within the region. The regional assessment has been updated to include design value rank, population served, area served, correlation between sites, and site removal bias. The results of these analyses are offered in both graphical and tabular formats. Further, a review of sites eligible for shutdown and an analysis of revenue and operation costs are provided. This assessment is intended to provide information on whether monitoring networks still meet the monitoring objectives, whether new sites are needed, whether existing sites are no longer needed, and whether new technologies are appropriate.

Based on federal monitoring requirements and data analyses, the document provides detailed conclusions broadly consisting of key findings, new priorities and important issues including the recurring concern of sufficient funding. Although the recommendations are non-binding, Wisconsin's air monitoring program uses this as a tool for prioritizing monitoring operations and budgeting in upcoming annual network assessments.

Ambient air monitoring network configuration and siting criteria

The EPA sets minimum network requirements in federal code. Monitoring beyond federal minimum requirements is conducted to provide better documentation of air quality in a particular community. For example, adequately defining the ambient ozone problem in any given area, especially the larger urban areas, generally requires additional monitors. Federal grants fund the majority of the DNR air monitoring network.

Operating within funding constraints, Wisconsin's air program continues to:

  • consolidate monitoring sites;
  • increase automation;
  • eliminate redundancies;
  • upgrade to higher-sensitivity monitors for reactive nitrogen and carbon monoxide; and
  • enhance the air toxics monitoring network.

We continue to work toward expanding network coverage in Wisconsin through partnerships with industry, Native American tribes and other entities.

Special studies

Special monitoring studies

Here you will find special air monitoring studies of emissions from agricultural operations, urban air toxics, polychlorinated biphenyls (PCBs) and other hazardous air pollutants.


Livestock fenceline ammonia and hydrogen sulfide monitoring study

This 2010 study investigated concentrations of ammonia and hydrogen sulfide around several Animal Feeding Operations (AFOs) in south central Wisconsin, including a large poultry operation, three dairies and a small confined swine operation.

Dairy and livestock air emission/odor project

This 2009 project was a joint effort between the Wisconsin Department of Agriculture Trade and Consumer Protection (DATCP) and DNR, and was partially funded through a USDA Conservation Innovation Grant (CIG). The project was a three year, $1.6 million demonstration of current technologies that focused on control of odor and concentrations of ammonia and hydrogen sulfide from agricultural operations.


Polychlorinated biphenyls are a legacy pollutant, which means they are most often found in contaminated sediment. However, PCBs are commonly found in ambient air as well.

Urban air toxics

The Urban Air Toxics program monitors a variety of heavy metals and both volatile and semi-volatile organic compounds on an on-going basis.

Volatile organic compounds (VOCs)

Vehicle exhaust is a major source of volatile organic compounds (VOCs), even in areas with a known major source.

Miscellaneous studies

Zip file that includes: studies on ambient atrazine; air quality forecasting; landfill monitoring at Portage, WI, and near Sarona, WI; June 20-25, 2002, ozone episode; urban leaf burning monitoring in Monona, WI; and ambient monitoring in Eagle River, WI.

Near-road network

U.S. Environmental Protection Agency near-road monitor program

Motor vehicle exhaust in the urban environment affects concentrations of various pollutants in ambient air. To better understand this impact, the U.S. Environmental Protection Agency (EPA) developed the near-road monitoring network as part of the 2010 NO2 NAAQS review. This required state and local air monitoring agencies to install near-road nitrogen dioxide (NO2) monitoring stations at locations where peak hourly NO2 concentrations are expected to occur. The Core Based Statistical Area (CBSA) of the Milwaukee metropolitan area qualified Milwaukee to have a near-road monitoring station installed.

Near-road monitor establishment

Near-road monitor near I-94 and College Avenue in Milwaukee.
Near-road monitor near I-94 and College Avenue in Milwaukee.

As required, from May 2012 to January 2014, DNR considered and tested several locations in and around the Milwaukee CBSA. Based on traffic volumes and preliminary analysis, the current College Avenue location was selected and Wisconsin began operating its near-road monitoring station on January 1, 2014. The station is located in Milwaukee County in close proximity to Interstate Highway 94 near the College Avenue exit.

The monitoring station measures fine particles (PM2.5), NO2 and carbon monoxide (CO) as required by EPA. Supplementary measurements of wind direction, wind speed and temperature are also collected to support analysis of the pollution measurements. All measurement equipment is connected to an on-site data logger where monitoring data is collected and transmitted continuously to DNR's central data system. Consistent with other monitoring stations, real time data is made available through the DNR WebMap and EPA’s AirNow webpage.

Pollutants measured

TThe EPA sets National Ambient Air Quality Standards (NAAQS) that states must adhere to for certain pollutants known as criteria pollutants. The near-road site currently measures three criteria pollutants and tests for numerous additional non-criteria pollutants utilizing Special Purpose Monitors.

Near-road monitor site

A view of I-94 from the roof of the near-road monitoring station, where air monitoring inlets collect ambient air samples.

Criteria pollutants
Monitoring equipment inside the near-road monitoring station.

Monitoring equipment inside the near-road monitoring station.

Nitrogen dioxide is one of a group of highly reactive gasses known as "oxides of nitrogen" (NOx). The EPA's NAAQS uses NO2 as the indicator for the larger group of nitrogen oxides. Nitrogen dioxide forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone and fine particle pollution, NO2 is linked with a number of adverse effects on the respiratory system.

Carbon monoxide is a colorless, odorless gas emitted from combustion processes. Nationally, and particularly in urban areas, the majority of CO emissions in ambient air comes from mobile sources. Carbon monoxide can cause harmful health effects by reducing oxygen delivery to the body's organs and tissues like the heart and the brain. At extremely high levels, CO can cause death.

Fine particles (PM2.5) are particulate matter that is 2.5 micrometers and smaller in diameter. These particles form as a result of chemical reactions of precursors such as sulfur dioxide (SO2), NOx, organic carbon, and ammonia. PM2.5 is considered an inhalable particle pollutant that can have adverse health effects on the respiratory and circulatory systems.

Current hourly values of these pollutants from the Near Road site can be viewed at Milwaukee County Nitrogen Dioxide, Milwaukee County Carbon Monoxide and Milwaukee County PM2.5.

Special Purpose Monitors (SPM)

The DNR also operates several Special Purpose Monitors (SPMs) at the near-road site. These SPMs measure black carbon (BC) [exit DNR], a by-product of combustion that may include diesel emissions, as well as ultraviolet-absorbing particulate matter (UVPM). Additionally there are monitors for measuring ultrafine particulate matter (<PM1) and benzene and toluene concentrations. This data will be used by EPA to better assess the health impacts of the near-road environment.

Nitrogen Dioxide and Carbon Monoxide - Wisconsin Near-road and National Trends

Since its establishment in 2014, the Wisconsin near-road monitoring site has not measured an exceedance of the NO2 or CO NAAQS. The maximum reported individual one-hour NO2 reading so far has been 61 parts per billion (ppb), well below EPA's national one-hour standard of 100 ppb.

National data indicates that Wisconsin and other states with a near-road air monitoring station are below the NAAQS 1-hr standards for NO2 and CO. This means that across the nation near-road sites are reporting NO2 and CO values well below the NAAQS.

Milwaukee College Ave. near-road monitoring station 1-hour daily max NO2 values

Milwaukee College Ave. near-road monitoring station 1-hour daily max CO values

Exceptional events

Exceptional events

Sometimes naturally-occurring events such as forest fires or wind storms can result in a violation of a National Ambient Air Quality Standard [exit DNR]. In these instances, emissions from anthropogenic sources such as cars, factories and power plants were not responsible for violation of the Air Quality Standard. The EPA then allows states to request to have the naturally-occurring event designated as an "exceptional event." If EPA approves the state's request, all high pollutant values associated with the event can be flagged by DNR and excluded from comparison with National Ambient Air Quality Standards.

On November 20, 2015, EPA proposed a revised Exceptional Events rule with new draft guidance [exit DNR].

The DNR conducted a thorough review of the new rule and guidance, and submitted comments to EPA on February 3, 2016. The comments are broken into four broad areas of concern:

  1. administrative burden on air agencies;
  2. consistency across EPA regions;
  3. EPA responsibilities and accountability; and
  4. insufficient and unclear requirements and definitions.

Pagami Creek fire event - September 2011

Industrial monitoring

Industrial monitoring

The DNR provides support and technical expertise to facilities that are required to do ambient air monitoring as part of a permit condition. Air monitoring staff review ambient air monitoring plans (AAMPs) and monthly data reports. They also conduct data consolidation/archival audits as well as annual instrument audits.

A large portion of the current industrial monitoring network in Wisconsin is related to industrial sand mines. Additional information can be found on our sand mining web pages.

Guidance documents and tools

The links below include information and guidance regarding DNR audit procedures for high volume samplers. Additionally, industrial operators will find information about operation of samplers (calibrations, verifications and routine operations). Forms are provided to use as-is, or to modify and use to suit an industrial operator's needs.

Last revised: Friday April 26 2019