Air monitoring is required under the federal Clean Air Act (CAA). Code of Federal Regulations, 40 C.F.R. Part 50 and 40 C.F.R. Part 58, detail the siting and operating of air monitoring sites and operating air monitoring instruments in a way to ensure that the data collected is valid.
State and Local Air Monitoring Stations (SLAMS)
The State of Missouri operates a network of about 50 ambient air monitoring sites, called State and Local Air Monitoring Stations (SLAMS). The main purpose of this air monitoring network is to determine whether areas in Missouri are meeting the primary National Ambient Air Quality Standards (NAAQS). These standards are established by EPA to protect human health effects and are available in the NAAQS Table.
Data from the monitoring network are sent to EPA’s national database of air monitoring data, called the Air Quality System (AQS). This data also helps develop information on air quality for the citizens of Missouri. Concentrations of most air pollutants are measured continuously, with hourly averages reported. A detailed description of the air monitoring network and demonstration that it is intended to meet all the ambient air monitoring federal requirements are included in an annual monitoring network plan.
Special Purpose Monitors (SPM)
In addition to the basic required monitoring sites, Missouri also operates special purpose monitors (SPM). For example, for short term air quality studies or instrument evaluation and monitors for trends in concentrations of toxic air pollutants at a site in St. Louis as a part of the National Air Toxics Trends Sites (NATTS) network.
Other Air Monitoring
Some industrial facilities in Missouri also conduct air monitoring near their facilities. This monitoring is done following quality assurance requirements reviewed and approved by the state. Site operation and instrument performance at these sites are periodically reviewed (audited) by the state. These industrial sites are also identified in the annual monitoring network plan. Data from these sites are also reported to the AQS database.