Ambient Air Monitoring in Connecticut

A photo of the CT DEEP Air Monitoring Station in Danbury, CT. DEEP monitors air quality to protect public health and the environment.  Air quality monitoring is crucial to determine compliance with the National Ambient Air Quality Standards (NAAQS) and to evaluate the effectiveness of air pollution control and abatement strategies. The criteria pollutants measured in Connecticut's ambient air monitoring network are ozone (O3), particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO).

DEEP maintains 14 air monitoring stations throughout Connecticut to measure the criteria air pollutants and additional pollutants of concern. These stations represent the majority of Connecticut's population and serve to characterize the ambient air quality across different scales of Connecticut. The details of the air monitoring network are described with the Air Monitoring Network Plan, which is updated yearly. A full assessment of the Air Monitoring Network is conducted every five years. 

Additionally, DEEP makes daily forecasts to help the public plan their day. These forecasts predict the ozone and particulate levels for cities and towns around the state. Ozone forecasts are limited to the summer season between May 1st to September 30th because ozone formation is linked to hot, sunny summer weather. Links to historical ozone data and health effects can be found on our Air Quality and Health web page.

2023 Air Monitoring Network Plan

2020 Air Monitoring Network Assessment

Air Monitoring Network and Community Based Monitoring Fact Sheet 

The below map shows the location of the 14 stations maintained by DEEP. The CASTNet station in Pomfret is maintained by the US Environmental Protection Agency (EPA).

A map showing the locations of the 15 air monitoring stations in Connecticut. 


 Content last updated July 27, 2023