The Clean Air Act requires EPA to revise the air quality standards based on review of the latest scientific information on known and potential human effects associated with PM (particle) levels typically found in ambient air. In this regard, EPA recently reviewed the air quality criteria and National Air Quality Standards (NAAQS) for PM and its serious health effects. Based on the review, EPA revised and promulgated two new standards for particles with aerodynamic diameter less than or equal to 2.5 micrometer (PM 2.5) and the regulatory requirements for monitoring the chemical composition and concentrations of these PM 2.5 such as selected ions, metals, carbon species, and organic compounds. In meeting the requirements to monitor and gather data on the chemical makeup of these PM, EPA is establishing a chemical speciation network consisting of 300 monitoring sites. These will be placed at various National Air Monitoring Stations (NAMS) and State and Local Monitoring Stations (SLAMS) across the nation. Also, 20 monitoring sites will be placed at existing Photochemical Assessment Monitoring Site (PAM). This Quality Assurance Guidance Project Plan (QAPP) focuses on required measures for ensuring that data of adequate quality are provided by the 54 team network sites.