Open Air Chicago Day Aggregations

Sensors deployed throughout the City by Open Air Chicago measuring fine particulate matter 2.5 (PM2.5) and nitrogen dioxide (NO2). All sensors collect data on PM2.5 and NO2. Six sensors also collect data on black carbon (BC) and current weather conditions.

24-hour mean measurements are calculated by averaging all measurements collected over a complete UTC day. For example, the 24-hour mean for 2026-01-01 aggregates all measurements from 00:00 UTC to 23:59:59 UTC on 2026-01-01.

There are related datasets linked below that show the individual measurements and aggregations by hour.

<b>Special Note: As of the launch date of this dataset, the black carbon modules are currently offline. All related metrics are unavailable until further notice and will appear as blank in the dataset.</b>

Some metrics have ready-to-use values directly from the sensor. No further processing occurs. Examples are temperature, relative humidity, and wind. Other metrics have raw data processed further in the Clarity cloud. We call these metrics "cloud-calibrated." Examples are PM2.5 and NO2, which have a global correction factor applied. Column names end in either .raw or .value. For direct-from-sensor metrics, raw and value are the same. For cloud-calibrated metrics raw is from the sensor and value is cloud-calibrated and different from raw.

For more information, please visit:  
www.clarity.io/blog/v2-1-pm2-5-global-calibration
www.clarity.io/blog/introducing-claritys-global-no2-calibration-model.

Metrics related to black carbon, ambient temperature, relative humidity, and wind speed and direction are for research purposes being conducted by UIC SPH. In addition to the 277 sensors deployed as part of the Open Air Chicago network, there are additional sensors installed at federal monitoring sites to inform the development of a potential local correction factor. 

This dataset is limited to measurements that have met Clarity's automated data quality control checks to ensure the data are high quality. For more information, please visit: https://click.clarity.io/knowledge/quality-control. If you are interested a dataset that includes invalidated data, please submit a data request at <a href="https://www.chicago.gov/city/en/depts/cdph/provdrs/health_data_and_reports/svcs/data-request-form.html" target="_blank">this link</a>.

Open Air Chicago is a citywide project consisting of 277 non-regulatory, air sensors installed in Summer 2025. It was founded by the Chicago Department of Public Health (CDPH) and the University of Illinois at Chicago School of Public Health (UIC SPH). The development of the network was supported by an advisory board and other partners, including the following: Alliance of the Southeast, Chicago Environmental Justice Network, Communities United, Grow Greater Englewood, Little Village Environmental Justice Organization, Neighbors for Environmental Justice, ONE Northside, Openlands. People for Community Recovery, Pilsen Environmental Rights and Reform Organization, Southeast Environmental Task Force, The Southwest Collective and the Westside Cultural Alliance, Chicago Department of Transportation, Cook County Department of Environment and Sustainability, Illinois Environmental Protection Agency, RHP Risk Management, University of Illinois Urbana-Champaign, Clarity Movement Company, and Illinois Public Health Institute.

Dr. Serap Erdal from UIC SPH was awarded two grants to support Open Air Chicago, which are: a) Erdal. S. Community-Driven Air Quality and Environmental Justice Assessment. Congressional Earmark Grant/National Institute of Standards and Technology. Grant No: 60NANB23D206, 10/1/2023-9/30/2026; b) Erdal, S. ComEd Hyperlocal Air Quality Assessment. RHP Risk Management/ComEd/Exelon, LLC. 1/16/2025-1/31/2026.

For more information on Open Air Chicago, please visit: <a href="https://www.chicago.gov/city/en/depts/cdph/supp_info/Environment/open-air-chicago.html" target="_blank">Open Air Chicago website</a>.

Tags: air-quality, air-quality-index, aqi, health, nitrogen-dioxide, particulate-matter, public-health, sensors, weather
Organization: City of Chicago