The DNREC Division of Air Quality operates a series of monitoring stations throughout the state. This monitoring network measures pollutants for which national air quality standards have been defined to protect public health. These are known as “Criteria Air Pollutants.”

The standards that the Delaware network measures for are set as part of the National Ambient Air Quality Standards (NAAQS). They include an adequate margin of safety to protect sensitive populations such as children and asthmatics.

The criteria air pollutants monitored are Ozone (O₃), Carbon Monoxide (CO), Nitrogen Dioxide (NO₂), Sulfur Dioxide (SO₂), Lead (Pb), and Particulate Matter, both fine particles (PM_2.5) and coarse particles (PM₁₀).

Data from the monitoring network is collected by DNREC for reporting to the public and the US Environmental Protection Agency.

About the Delaware Air Quality Monitoring Network

The data collected from these monitoring stations is stored in a central DNREC data system and, after quality assurance is performed, reported to the EPA’s National Air Quality Database. Data is publicly available through the EPA’s Air Now website. The raw data is posted as part of the Delaware Open Data Portal.

The data is also presented on an hourly basis on the DNREC Air Monitoring application. Data from monitoring sites supports special projects by DNREC undertaken to address concerns of citizens, evaluate new technology, or address changing EPA rules. Special projects may involve a variety of tools to study air quality or even the use of a Moveable Monitoring Platform.

Monitoring stations are placed in locations based on factors that include population data, meteorological conditions, locations of pollution-emitting industry, and historical air quality trends. The state performs periodic assessments of its network every five years to determine if the network meets the state’s monitoring objectives. The most recent review was completed in 2020.

The state submits an annual monitoring plan for EPA approval each year. The plan includes the results of the most recent five-year assessment, describes the network and describes any planned changes. The most recent approved plan is the 2023 Delaware Air Monitoring Network Description.

The Delaware air quality monitoring network includes permanent monitoring stations in all three counties. Eight of the permanent monitoring stations measure multiple pollutants with a focus on ozone monitoring. Three measure only particulate matter. The Wilmington site monitors all criteria air pollutants and additional pollutants of interest.

Annual Air Quality Reports

The Annual Air Quality Reports serve as a resource for information on Air Quality issues in Delaware. The reports focus on Delaware’s air quality status and trends for pollutants shown to threaten human health and welfare for which standards have been set by the EPA, known as the “criteria pollutants.” Information is also provided on some pollutants monitored without standard criteria, such as air toxics.

In additional to air monitoring the reports include discussions on sources of air pollution, inventory data related to the compounds responsible for forming ozone and PM_2.5 pollution, and air quality issues related to climate change.

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