Quality Assurance

This page last reviewed March 17, 2014

ARB is the governmental agency delegated under law with the authority and responsibility for collecting ambient air quality data as directed by the Clean Air Act of 1977 and Clean Air Act Amendments of 1990.  ARB's Quality Management Branch (QMB) provides underlying quality assurance of ambient air data collected in California.  QMB is directly responsible for the precision and accuracy of all data generated and collected by the Monitoring and Laboratory Division, and indirectly responsible for precision and accuracy of all data collected by local and private air monitoring agencies in California's air monitoring network.  QMB performs a complex array of quality assurance and quality control activities to ensure that ambient air data are in compliance with all applicable quality assurance requirements established by State and federal monitoring regulations and guidance documents.

ARB is required by federal regulations to provide quality assurance oversight to local air monitoring organizations within ARB's Primary Quality Assurance Organization (PQAO) to ensure that consistent procedures are followed to produce data of similar quality.  A PQAO is a monitoring organization or a coordinated aggregation of such organizations that is responsible for a set of air monitoring stations that monitor the same pollutants and for which data precision and accuracy assessments can logically be pooled.  Each criteria pollutant sampler/monitor at a monitoring station in the State and Local Air Monitoring Station Network must be associated with one, and only one, PQAO.  Measurement precision and accuracy among all air monitoring stations in a PQAO is expected to be reasonably homogeneous based on the following five factors:

  1. Operation by a common team of field operators according to a common set of procedures;
  2. Use of a common quality assurance project plan (QAPP) or standard operating procedures (SOPs);
  3. Common calibration facilities and standards;
  4. Oversight by a common quality assurance organization; and
  5. Support by a common management, laboratory or headquarters.

The U.S. Environmental Protection Agency (U.S. EPA) designated ARB as PQAO for all of California with the exception of the Bay Area Air Quality Management District, the South Coast Air Quality Management District, and the San Diego County Air Pollution Control District.  ARB's PQAO consists of ARB and 32 local air monitoring organizations throughout California.  ARB and all monitoring organizations comprising ARBís PQAO are expected to follow, to the extent practical, the five common factors listed above.  The 21 monitoring organizations listed below are those which collect ambient air monitoring data in ARB's PQAO.

Antelope Valley Eastern Kern Great Basin Imperial Lake
Mendocino Mojave Desert Monterey Bay North Coast Northern Sierra
Northern Sonoma Placer Sacramento San Joaquin San Luis Obispo
Santa Barbara Shasta Siskiyou Tehama Ventura

Roles and Responsibilities

To address the five common factors listed above and ensure compliance with State and federal air monitoring requirements, ARB works collaboratively with each monitoring organization in its PQAO and U.S. EPA to define each agency's respective roles and responsibilities with regard to the operation of the State's ambient air monitoring network.  Finalized Roles and Responsibilities documents are listed below.

Quality Management Documents

All monitoring organizations within ARB's PQAO are required to utilize and follow ARB's quality management documents [Quality Management Plan(QMP), QAPPs, and SOPs] for each primary area of operation or submit alternative documents to ARB and/or U.S. EPA for review and approval.  The Quality Management Document Repository listed below identifies specific documents utilized by ARB, monitoring organizations within ARB's PQAO, and other participating PQAOs.

The Quality Assurance Manual listed below is comprised of six volumes that describes ARB's Quality Assurance Program:

The U.S. EPA Quality Assurance Handbook volumes listed below are guidance documents for air pollution measurement systems.   Volume II is dedicated to ambient air quality programs and associated data collection activities.  Volume IV provides information and guidance specific to the operation of meteorological equipment and associated data generation:

The following checklists are utilized by ARB to facilitate the review of QMPs, QAPPs, and SOPs prepared by monitoring organizations within ARB's PQAO:

The link below provides information related to precision and accuracy results for individual air monitoring organizations:

The link below provides a summary of the quality of ambient air data in quantifiable terms and an overview of various quality assurance and quality control activities.

Performance Audits

Annually, ARB conducts performance audits of gaseous, particulate matter, and meteorological measurements conducted at air monitoring sites throughout ARB's PQAO to determine the accuracy of monitoring equipment in accordance with all applicable requirements, including 40 CFR, Part 58, Appendix A.  Gaseous audits are conducted using National Institute of Standards and Technology (NIST) traceable gaseous standards to verify the accuracy of automated methods and to ensure the integrity of the sampling system.  The accuracy of particulate samplers is determined by comparing the instrument's flow rate to a NIST traceable orifice or flow meter.  These audits are conducted semi-annually, approximately six months apart.  The accuracy of meteorological sensors is determined by comparing air monitoring station equipment to independent audit equipment and certified wind speed anemometers.  Audit results are evaluated to determine if the percent difference is within the applicable State and federal audit acceptance criteria.  Field and laboratory performance audits are routinely conducted to ensure the accuracy of data generated.  The link above provides additional information about each type of audit performed, including Through-the-Probe, Flow, Laboratory, and Meteorological.

Technical System Audits

A Technical System Audit (TSA) is an on-site inspection and review of an organization's entire air monitoring program.  The audit includes a review of sample collection, sample analysis, and data processing procedures; facilities; documentation; and staff duties and training to assure compliance with all applicable air monitoring requirements.  ARB is responsible for conducting TSAs of ambient air monitoring organizations within its PQAO at a frequency of every three years.  The link above provides additional information related to TSAs.  The questionnaire listed below is utilized to facilitate the TSA process.

Corrective Action Notification

The Corrective Action Notification (CAN) process was developed for ARB's PQAO to document, investigate, correct, and reduce the recurrence of air monitoring issues that may impact or potentially impact data quality, completeness, storage, or reporting.  The objective of the CAN process is to improve the quality of air monitoring data and to ensure compliance with State, federal, and local requirements.  The link above provides additional information related to the CAN process, including the CAN SOP and CAN Form.

Standards Laboratory

As defined in 40 CFR, Part 58 Appendix A, Section 3.1.1, one of the factors considered in defining a PQAO is the utilization of common calibration facilities and standards.  The use of common calibration facilities and standards helps ensure the data produced are of similar quality.

ARB's Standards Laboratory performs certification and verification services of calibration instruments, gases, and devices for ARB and local air districts at no cost.  Calibrations and certifications are performed for ozone and flow rate transfer standards, certifications are performed for compressed gas cylinders, and verifications are performed for ozone and flow rate primary standards.  In addition, multi-point calibrations of pressure transducers, stand-alone pressure gauges, barometers, and temperature probes are conducted.  The link above provides additional information related to the Standards Laboratory.


ARB recognizes that continuing education and training are a critical component of maintaining continuity and an effective and efficient quality assurance program.  ARB's Monitoring and Laboratory Division is developing training modules for air monitoring staff and management at all levels.  The modules are designed to emphasize the fundamentals in key areas of ambient air monitoring.  The link above provides additional information related to training.

Join the PQAO Contact List Serve

This list is open to the public. Anyone interested in receiving PQAO related information may join this list serve.  The PQAO Contact List Serve will be used by ARB to share pertinent air monitoring information with the local air monitoring organizations and other interested parties.

A primary contact for each monitoring organization was designated and is responsible for sharing information within their respective organization.

For further information contact: Michael Miguel, Chief, Quality Management Branch at (916) 322-0960

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