Data and Tools
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What does the POC number refer to?
POC is the Parameter Occurrence Code and is used to uniquely identify a monitor if there is more than one device measuring the same pollutant at a site. The POC number assignment is somewhat arbitrary and varies between sites that are maintained by different state and local agencies. POC designation…
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Can I include my monitor in the EPA’s monitoring network?
The monitors that make up our monitoring network follow stringent siting and quality assurance criteria and are maintained by state and local agencies. You can read about the monitoring network requirements in 40 CFR part 58. Some states are also beginning to supplement their monitoring network with low-cost sensors; however…
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Who decides where monitors get placed?
States typically decide where monitors are placed based on areas of relatively high population and/or areas believed to have relatively higher pollutant concentrations. Each state is responsible for developing its own monitoring plan, which is then reviewed and revised every five years. Follow this link for guidance on state and…
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Why do you use the highest summary statistic (AQI/concentration) among all monitors in an area to represent that area (as opposed to using an average)?
For convenience, we customarily use county and CBSA area definitions for aggregating spatially. And we do typically use the highest daily AQI value among all monitors in each area to represent that area. This practice is consistent with the national ambient air quality standards which strive to ensure that all…
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Do you provide rankings of cities or states based on air quality?
We do not rank cities or states by air quality, but you can use the AirCompare website to compare air quality among counties in the U.S. based on factors that have been shown to increase risk from air pollution. Return to Frequent Questions about AirData
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Do you provide outdoor air monitoring data aggregated at the state level?
We don't aggregate concentration data at a state level, primarily because it can, and does, vary widely across any given state. That's why you see monitor-level, county-level, and CBSA-level aggregates on the website. Return to Frequent Questions about AirData
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Are monthly aggregates available for outdoor air monitoring data?
No, we provide daily and annual summary files. Return to Frequent Questions about AirData
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When will outdoor air monitoring data for the entire year be available?
EPA regulations give reporting organizations (states, tribes, and local agencies) 90 days following the end of a calendar quarter to submit their data to EPA's Air Quality System (AQS). For Q4 data, reporting organizations have until the end of Q1 (March 31) in the next year to submit to AQS…
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Why isn’t recent outdoor air monitoring data available? Where can I find that?
EPA regulations give reporting organizations (states, tribes, and local agencies) 90 days following the end of a calendar quarter to submit their data to AQS to allow time for analysis and quality assurance, though many reporting organizations submit data prior to the 90-day deadline. Even so, at any point in…
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Why do the outdoor air monitoring data summaries only go back to 1980? Isn’t older data available?
While older monitoring data are available in AQS, we use 1980 as the first year for tracking trends because that year marks the beginning of nationally consistent operational and quality assurance procedures for air quality monitoring, particularly for ozone. PM10 monitoring began in many areas around 1987-1988. PM2.5 monitoring was…
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Do you have outdoor air monitoring data for all counties in the U.S.?
No, approximately 1,000 out of the roughly 3,000 U.S. counties have monitoring data. Return to Frequent Questions about AirData
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Do I need to request permission to use the monitoring data and graphics from the AirData website in my research or publication?
The ambient monitoring data in EPA’s Air Quality System (AQS) are public domain. You are welcome to download the data and use freely, without submitting a request. Return to Frequent Questions about AirData
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How do I cite data and graphics obtained from the AirData website?
Please use the following citation: US Environmental Protection Agency. Air Quality System Data Mart [internet database] available via https://www.epa.gov/outdoor-air-quality-data. Accessed Month DD, YYYY. Return to Frequent Questions about AirData
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What is the best way to access outdoor air monitoring data?
By Data Type – it depends on what you need. Current and forecast data and maps AirNow.gov Daily summaries of recent and historical data Historical - Pre-generated files of Daily Summary Data Recent and Historical - AirData Air Quality Index (AQI)-related reports and visualizations Annual summaries Pre-generated files of Annual…
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Frequent Questions about AirData
outdoor air quality data faqs
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Interactive Map of Air Quality Monitors
map of air quality monitors
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Assessment of PM2.5 FEMs Compared to Collocated FRMs
This memorandum describes a one-page technical report that assesses the comparability of a PM2.5 continuous monitor when collocated with an FRM sampler.
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2016 Revisions to the Exceptional Events Rule: Update to Frequently Asked Questions
This September 11, 2018, document replaces the “Interim Exceptional Events Rule Frequently Asked Questions” document posted on May 14, 2013.
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Exceptional Events Submissions Table (2016 Rule)
This table contains examples of air agency submitted exceptional events demonstrations and responsive EPA decision documents that have been prepared and/or acted upon under the 2016 Exceptional Events Rule
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Exceptional Events Documents Ozone - Pennsylvania
Exceptional Events Documents Ozone - Pennsylvania