Particulate Matter Pollutant Monitoring

This page last reviewed January 10, 2014

The California Air Resources Board monitors particulate matter pollutants to demonstrate attainment or non-attainment of national and state ambient air quality standards (standards).  Particulate monitoring can be divided into two main categories: monitoring of particulate matter with an aerodynamic diameter of 10 microns or less (PM10) and monitoring for particulate matter with a diameter of 2.5 microns or less (PM2.5). PM2.5, of course, is a constituent of PM10. The CARB particulate matter monitoring programs under these two programs are described below.

PM10 Monitoring

PM10 is a mixture of various substances. These substances occur in the form of solid particles or as liquid drops. Some particles are emitted directly into the atmosphere. Other particles result from gases that are transformed into particles through physical and chemical processes in the atmosphere. A variety of emission sources and meteorological conditions contribute to ambient PM10.

PM10 Mass - The PM10 standards are expressed as a weight of PM10 particles per volume of air (micrograms per cubic meter). PM10 mass is collected using a high volume sampler (40 cubic feet per minute) and a quartz fiber filters (8" x 10"). The standards do not consider the size distribution or the chemical make-up of the particles, although these are important factors in terms of control strategies and of the health risks associated with PM10.

Ion Analysis - This program measures some of the major secondary components of PM10. Secondary PM10 is not emitted as particles but is formed through chemical reactions in the atmosphere. Knowledge of the components of PM10 can indicate the source of the PM10 and provide insight into how to control PM10. The inorganic ion analyses of PM10 are performed at the request of the Planning and Technical Support Division (PTSD). Chloride (Cl-), nitrate (NO3-), sulfate (SO42-), ammonium (NH4+), and potassium (K+) are routinely measured from samples collected in the network.

PM2.5 Monitoring

PM2.5 particulate matter, called "fine" particulate, is primarily a result of combustion products emitted into the atmosphere as well as those particles that are formed in the atmosphere from gaseous pollutants as a result of atmospheric chemistry (secondary formation). Generally, the fine particulate poses a greater health risk because these particles can deposit deep in the lung and contain chemicals that are particularly harmful to health. In addition to health impacts, these particles can reside in the atmosphere for long periods of time and are the main contributors to reduced visibility.

PM2.5 Mass - PM2.5 mass concentrations are measured to determine attainment status for areas in California to the federal and state ambient air quality standards. Whereas PM10 mass is collected using a high volume sampler and quartz fiber filters, PM2.5 mass is collected using a low volume sampler (16.7 liters per minute) and a small (47 mm) Teflon filter. Because much less mass is collected by the PM2.5 sampler, the samples are weighed to the nearest microgram (one millionth of a gram) by special, ultra-sensitive balances under exacting conditions. Extreme care must be taken to insure accurate results. Laboratories performing these analyses must be pre-qualified and are monitored to insure acceptable performance.

PM2.5 Chemical Speciation Monitoring

The U.S. EPA requires the monitoring of the chemical composition of PM2.5 particulate matter for use in health studies and to determine appropriate control measures. Currently, the chemical speciation samples collected at the National Air Monitoring sites (NAMS) in California are analyzed by the EPA contract laboratory. The samples collected at the State and Local Air Monitoring sites (SLAMS) are analyzed by the CARB laboratory. Although additional chemical constituents may be monitored (levoglucosan, for example), the minimum target list identified by the EPA includes elemental analyses by X-Ray Fluorescence, ion analyses (nitrate, sulfate, ammonium, potassium and sodium) and elemental / organic carbon as well as mass. The CARB laboratory undergoes annual system and performance audits by the U.S.EPA to insure that produced data for this program is of acceptable quality.

Elemental Analysis - After collection on a Teflon filter and determination of mass collected, the samples are submitted for X-Ray Fluorescence analysis. This analysis determines the concentration of 28 elemental constituents in the PM2.5.

Ion Analysis - After nitric acid denuded collection on a nylon filter, the water-soluble ionic constituents are extracted and analyzed by ion chromatography.

Elemental / Organic Carbon Analysis - After collection on a cleaned quartz fiber filter, the determination of the organic and elemental fractions of the carbon collected is made with thermal-optical pyrolysis. The organic fraction of the carbon is a result of direct emissions into the atmosphere as well as organic compounds formed through atmospheric reactions. The elemental carbon is solely a result of direct emissions, usually from combustion sources. The determination of the elemental and organic fractions is method dependent, so careful control of the analysis conditions is required. 

Sampling / Monitoring

Monitoring Activities summarizes the network and the monitoring methods for PM10 and PM2.5. It includes sampling schedules, number of sites operating in the State, methodology used by the ARB, U.S. EPA reference method and data availability.

The particulate matter program follows a daily, three-day, six-day, or twelve-day ambient air monitoring schedule, which is derived from U.S. EPA's monitoring sampling schedule calendar

Laboratory Standard Operating Procedures (SOP)

Each method used to generate laboratory data has a written SOP. These procedures are followed each time the method is used to produce data for record. The following is a list of the laboratory SOPs currently used in the analysis of particulate pollutants.

  • SOP MLD005 - Acid Digestion and Analysis of Metals from the Total Suspended Particlates(TSP)
  • SOP MLD007 - PM10 Anions Sulfate (SO42-), Nitrate (NO3-), and Chloride (Cl-) by Ion Chromatograph (IC)
  • SOP MLD016 - PM10 Filter Mass Analysis and Extraction for IC Analysis
  • SOP MLD023 - PM10 Cations Ammoniun (NH4+) and Potassium (K+) by IC
  • SOP MLD034 - Elemental Concentrations by Energy - Dispersive X-Ray Fluorescent (XRF) Spectroscopy
  • SOP MLD055 - PM2.5 Mass in Ambient Air by Gravimetric Analysis
  • SOP MLD062 - Filter and Canister Preparation for PM2.5 Speciation Samples
  • SOP MLD064 - Anions and Cations in PM2.5 Speciation Samples by Ion Chromatography
  • SOP MLD065 - Organic and Elemental Carbon Analysis of Exposed Quartz Microfiber Filters

Quality Assurance

The Quality Assurance Section conducts field and laboratory performance audits to ensure the accuracy of the particulate matter pollutant data generated by ARB and local air quality agencies.  Information is available on the following topics:

Publications and Downloadable Files

June 2011 report on Arvin Special Purpose PM2.5 Monitoring Project (pdf - 1202KB)

Effects of Environmental Conditions on Particulate Nitrate Stability During Post Sampling Phase, Gerhard H. Achtelik, Jr.and Jim Omand. Technical paper presented at a International Specialty Conference, PM2.5: Fine Particle Standard, Long Beach, California, January 28-30, 1998. The conference was cosponsored by the AW&MA, the U.S. EPA, and the U.S.DOE.


This study was designed to evaluate the stability of PM2.5 particulate nitrate during the post sampling period. Four samples were collected per sampling run following instrument guidelines similar to those described in the particulate matter federal reference method. One of the four samples was extracted on-site and was used to represent a "no losses" category against which one could compare the effect of different post sampling environmental conditions. The remaining samples were exposed to various environmental conditions prior to extraction. The post sampling test conditions were storage temperature, storage time and open versus closed container. The post sampling test conditions were among those permitted in the operating parameters for filter handling described in the U.S. EPA's PM2.5 NAAQS regulations. The nitrate values were evaluated by regression analysis for similar environmental conditions. This study suggests that particulate nitrate losses occur if filters remain on samplers for prolonged periods of time after sampling. Losses increase as the filters are exposed to increased temperature. The study suggests that placing filters in closed containers and a cool environment can significantly reduce nitrate losses.

PM10 Mass Analysis System Audit Findings: A Prelude to PM2.5 (Fine) Mass Analysis, Thomas J. Pomales. Technical paper presented at the AWMA's 90th Annual Meeting and Exibition,Toronto, Ontario, Canada, June 8-13, 1997.


During 1992, the California Air Resources Board's (CARB) Monitoring and Laboratory Division initiated system audits for laboratories conducting PM10 mass analysis as data-for-record. The audits of the mass determinations complement ongoing performance audits of field samplers which began in1985 and provide a complete assessment of PM10 mass data. This paper presents the CARB's findings of the PM10 mass analysis system audits and highlights the most common problems encountered by mid- to small-sized organizations. Given the discrepancies that we discovered and the possibility of new and different requirements for a fine particulate National Ambient Air Quality Standards (NAAQS), laboratories need to be better prepared to meet the challenge of performing consistent particulate matter mass weighings in the future.

The system audits include an assessment of filter handling and storage, standard weight checks, balance calibrations, equilibration techniques, tare and gross weight checks (duplicate weighings) and data management. They also include performance audits of the balances used to weigh the PM10 filters.

This paper looks at the PM10 mass analysis system audit requirements, history, description, findings and implications. The paper identifies the most common problems encountered by auditors, including poor recordkeeping; inadequate filter equilibration (relative humidity and temperature); and missing duplicate weighings and balance calibrations. These deficiencies have resulted in the invalidation of several years of valuable PM10 data. Avoiding these problems in the early stages of the PM2.5(Fine) mass analysis program is critical and will prevent valuable data from being invalidated.

Evaluation of Fine Particulate Samplers (PM2.5) in an Area of Volatile Constituents, Jeff P. Cook and William E.Oslund. Technical paper presented at the AWMA's International Specialty Conference Particulate Matter: Health and Regulatory Issues, Pittsburgh, Pennsylvania, April 4-6, 1995.


A National Ambient Air Quality Standard (NAAQS) for particulate matter equal to or less than 2.5 microns in diameter is being considered by the United States Environmental Protection Agency (U.S. EPA). Particulate matter of this size is commonly referred to as PM2.5 or, more generally, "fine" particulate matter. PM2.5 matter found in California can be volatileand water soluble, complicating sampling techniques. In order to investigate potential sampling methodologies for fine particulate, the U.S.EPA funded a field study conducted by the California Air Resources Board (ARB) between November 1994 and March 1995 in Bakersfield,California.

Wintertime atmospheric conditions in Bakersfield include persistent fog, temperatures in the near freezing range, PM10 concentrations ranging up to 300 micrograms/m3 and predominant concentrations of volatile compounds, such as ammonium nitrate and carbon in the total PM10 massmeasurements.

This paper presents the initial results of the 1994-95 Bakersfield winter particulate matter field study. A total of 16 samplers representing a variety of existing, modified and newly designated equivalent samplers, were sited in parallel and results for both PM10 and PM2.5 measurements were compared. We found that losses from evaporation and other mechanisms can lead to significant particulate matter mass loss during and after sampling. Understanding and addressing these losses are criticalto achieving a consistent measurement of PM2.5. These factors must be addressed as the U.S. EPA proceeds to identify reference or equivalent samplers for a possible fine particle NAAQS.

Voyager Data Files

  • Bakersfield Particulate Data - PKWare zipped file containing particulate air pollutants data and meteorological data collected at the Bakersfield - California Avenue site from November 19, 1994 through March 31, 1995. The principal objective of the Bakersfield Winter PM Study was to examine the performance of a variety reference and non-reference PM10 samplers and several PM2.5 samplers in an environment and during a season that would challenge any sampler. In addition to a meteorological system, 12 integrated particulate samplers and four continuous particulate monitors were operated in the study. The integrated sampling was performed every three days. The data were evaluated in a paper published by the Air & Waste Management Association in; Particulate Matter: Health and Regulatory Issues, VIP49, "Evaluation of Fine Particulate Samplers (PM2.5) in an Area of Volatile Constituents." (,571K)
  • Statewide Particulate Data - PKWare zipped file containing Size Selective Inlet (SSI) High Volume Sampler mass and ion data and Dichot mass data for a period from October1990 to March 1994. The file contains SSI chloride,nitrate, sulfate, ammonium, potassium and total mass data (total is measured); and Dichot fine, coarse and total mass data (total is sum of fine and coarse). (, 91K)
  • Statewide Particulate and PAMS HC Data - PKWare zipped file containing preliminary data for air pollutants and pollutant precursors sampled at seven California sites from June1,1993 to October 30, 1993. The Voyager file was used as a quality assurance tool to review the hydrocarbon data for year zero of the U.S. EPA mandated Photochemical Assessment Monitoring Stations (PAMS) program. The data taken during the Summer of 1993 will be used to assess the California Air Resources Board's monitoring capability and preview the ambient hydrocarbon patterns. (, 185K)

Related Links
PM Home Page - ARB's Main Website for Dissemination of PM 2.5 Information