Photochemical Assessment Monitoring Stations (PAMS)

Background

The PAMS network is an ozone precursor monitoring network operated by state and local agencies.  The PAMS program was originally started in the early 1990s to meet the requirements of Section 182(c)(1) of the Clean Air Act (CAA). Significant revisions to the PAMS requirements (found in 40 CFR part 58, Appendix D) were made as part of the 2015 Ozone National Ambient Air Quality Standard (NAAQS) review. The revised PAMS requirements call for ozone precursor measurements to be made at existing NCore sites (a multi-pollutant monitoring network also required in 40 CFR part 58) in Core Based Statistical Areas (CBSAs) with a population of one million or more . The main objective of the required PAMS sites is to develop a database of ozone precursors and meteorological measurements to support ozone model development and track the trends of important ozone precursor concentrations.

Each required PAMS site is expected to measure:

  • Hourly averaged speciated volatile organic compounds (VOCs),
  • Three 8-hour averaged carbonyl samples per day on a 1 in 3 day schedule, or hourly averaged formaldehyde,
  • Hourly averaged O3,
  • Hourly averaged nitrogen oxide (NO), true nitrogen dioxide (NO2), and total reactive nitrogen (NOy),
  • Hourly averaged ambient temperature,
  • Hourly vector-averaged wind direction,
  • Hourly vector-averaged wind speed,
  • Hourly average atmospheric pressure,
  • Hourly averaged relative humidity,
  • Hourly precipitation,
  • Hourly averaged mixing-height,
  • Hourly averaged solar radiation, and
  • Hourly averaged ultraviolet radiation.

Sites and Data

The following links can be used to collect information on the number and locations of PAMS sites and to download monitoring data.

Map of PAMS Sites

Quality Assurance and Other Guidance Documents

This section contains links to EPA guidance documents intended to assist monitoring agencies as they implement the PAMS requirements.

Model Quality Assurance Project Plan (QAPP)

Technical Assistance Document (TAD)

Target VOCs

Other Documents

Unified Ceilometer Network (UCN)

Model Standard Operation Procedures

This section contains links to guidance on methods used in the PAMS program.

Enhanced Monitoring Plans

In addition to the required PAMS sites, the PAMS requirements also call for each state with nonattainment areas classified as moderate or above for any ozone NAAQS and states in the Ozone Transport Region to develop and implement an Enhanced Monitoring Plan (EMP). The objective of EMPs is to better understand ozone formation in specific areas through enhanced ozone and ozone precursor monitoring activities.

Presentations and Training

Below are PAMS presentations from the 2016 National Monitoring Conference:

Special Studies

DART

Ambient Monitoring Technology Information Center (AMTIC)

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Last updated on April 1, 2025