Air Quality Monitor
A device that measures pollutant concentrations in ambient air, operated by government agencies as part of the national monitoring network.
Detailed Explanation
Air quality monitors are precision instruments that measure the concentration of specific pollutants in the ambient (outdoor) air. The US air quality monitoring network consists of over 4,000 monitors operated by state, local, and tribal agencies under the oversight of the EPA. Monitors use different measurement methods depending on the pollutant: PM2.5 monitors typically use Federal Reference Method (FRM) gravimetric samplers or Federal Equivalent Method (FEM) continuous monitors; ozone is measured by ultraviolet photometry; and gases like NO2, SO2, and CO are measured by chemiluminescence, ultraviolet fluorescence, and infrared absorption, respectively. Monitor placement follows strict siting criteria specified by the EPA to ensure data quality and representativeness. In recent years, low-cost air quality sensors (such as PurpleAir) have proliferated, giving individuals the ability to monitor local air quality. However, these consumer sensors are less accurate and less reliable than regulatory-grade monitors, especially at extreme temperatures and humidity levels. AirHistory uses only data from the EPA's official monitoring network (AQS) because it meets rigorous quality assurance standards. The number and distribution of monitors in a county affects data completeness, rural areas typically have fewer monitors, which is why AirHistory covers approximately 1,000 counties rather than all 3,000+ US counties.
Related Terms
EPA Air Quality System (AQS)
The EPA's national database of ambient air quality data collected from monitoring stations across the United States.
Air Quality Index (AQI)
A standardized EPA scale from 0 to 500 that communicates daily air quality and associated health risks.
Criteria Pollutants
The six common air pollutants regulated by the EPA under the Clean Air Act: ozone, PM2.5, PM10, CO, NO2, and SO2.
PM2.5 (Fine Particulate Matter)
Airborne particles smaller than 2.5 micrometers in diameter, small enough to penetrate deep into the lungs and enter the bloodstream.
Frequently Asked Questions
A device that measures pollutant concentrations in ambient air, operated by government agencies as part of the national monitoring network.
Air quality monitors are precision instruments that measure the concentration of specific pollutants in the ambient (outdoor) air. The US air quality monitoring network consists of over 4,000 monitors operated by state, local, and tribal agencies under the oversight of the EPA. Monitors use different measurement methods depending on the pollutant: PM2.5 monitors typically use Federal Reference Method (FRM) gravimetric samplers or Federal Equivalent Method (FEM) continuous monitors; ozone is measured by ultraviolet photometry; and gases like NO2, SO2, and CO are measured by chemiluminescence, ultraviolet fluorescence, and infrared absorption, respectively.
this entity is one of the U.S. air quality and pollution monitoring concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the EPA Air Quality System (AQS) data behind every per-entity page on the site.
In the the EPA Air Quality System (AQS) data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.