Accuracy assessments indicate the agreement between an analyzer measurement and a known audit standard concentration for continuous analyzers, or the agreement between an observed value and a known or reference value for manual methods. Accuracy Data record is uniquely identified by the combination of monitor, audit class, accuracy type, date, and Accuracy Audit ID Number.

Accuracy records are similar to calibration--up to five runs that categorize “Actual” values and “Indicated” values. Actual values are from the primary analyzer, while Indicated values are from some other external reference device. The Accuracy Report provides an output of raw accuracy value pairs and their percent differences. The data is grouped by Parameter, Tribal Area or State, and Reporting Organization.

The PARS Accuracy Editor (Figure 21) lists parameters in a table along with their Duration Code, Accuracy Date, and Accuracy Audit Number. The parameter that is selected (by clicking Select in the left column of the table) will be displayed below the table with the following information:

Accuracy Test Information

• Accuracy Date: The calendar date for which the accuracy audit information pertains.
• Accuracy Audit Number: A sequentially assigned number used to identify a particular precision check from others, when multiple checks are performed on the same day
• Accuracy Type: A description of the type of accuracy test performed
• Local Primary Standard: A description of the source of the local primary standards
• Local Standard Expiration Date: The expiration date for the local primary standard
• Audit Sample Identifier
• Audit Scheduled Date
• Audit Type: Description of who performed the audit and how the audit standard was certified
• Audit Class: Description of the class of audit taken at the monitor
• Audit Type: Description of who performed the audit and how the audit standard was certified

Monitor Information

• Parameter: The code assigned to the parameter measured by the monitor. (A “monitor” in AQS represents not a device but the pollutant measured by a device.) Parameters may be pollutants or non-pollutants.
• Duration Code: The length of time (interval) used to acquire raw samples that are analyzed by monitors
• Parameter Type: A description of the type of parameter (e.g., ozone)
• Unit Code: AQS code for the standard parameter unit (e.g., ppm)
• POC: Parameter Occurrence Code or Pollutant Occurrence Code, an identifier used to distinguish between multiple monitors at the same site that are measuring the same parameter. For example, the first monitor established to measure carbon monoxide (CO) at a site could have a POC of 1. If an additional monitor were established at the same site to measure CO, that monitor could have a POC of 2. However, if a new instrument is installed to replace the original instrument used as the first monitor, that would be the same monitor and it would still have a POC of 1.

For criteria pollutants, data from different sampling methods should only be stored under the same POC if the sampling intervals are the same and the methods are reference or equivalent. For sites where duplicate sampling is being conducted by multiple agencies or by one agency with multiple samplers, multiple POCs must be utilized to store all samples.

For non-criteria pollutants, data from multiple sampling methods can be stored under the same POC if the sampling intervals are the same and there is only one sample for the time reported. If multiple open path monitors are reporting data for the same parameter, each open path would be assigned a different POC.

• Method Code: Identifies the particular method for collecting and analyzing a precision check value
• State Code: A Federal Information Processing Standards (FIPS) code that identifies one of the 50 states, U. S. territories, Washington, DC, or foreign countries. For batch loading data formats only, it may be set to “TT” to indicate that the County Code/Tribal Code field contains a Tribal Code.
• County/Tribal Code: A Federal Information Processing Standards (FIPS) code that identifies a county, or other geo-political entity, such as tribe, parish or independent city. For foreign countries, it identifies the geo-political equivalent to U. S. states, such as Mexican states or Canadian provinces.
• Site Code: A numeric identifier (ID) that uniquely identifies each air monitoring site within a county, and if it is a tribal site, within all counties included in a tribal area. There is no requirement that Site IDs be assigned continuously or in any particular order. Regional or local organizations are thus free to allocate Site IDs in any way they choose, as long as there is no duplication within a county or the counties that include a common tribal area.

A specific Site ID is associated with a specific physical location and address. Any change in address requires a new Site ID to be assigned. This address change could include a change from the roof of one building to another. A change in location on the same roof should not normally require a new Site ID. Although an address change would routinely mean a new Site ID, some changes that do not change the site's location in respect to surrounding sources and its measurement scale would require no change. An EPA regional office should be consulted for assistance in determining whether a new site ID is required.

If a new Site ID is needed for a site not operated by the air pollution control agency, that agency should be contacted to assist in the ID assignment, to ensure that the ID is unique within the county and, if appropriate, the adjoining counties sharing a common tribal area. In other words, when a new Site ID is assigned, it must be different from any other Site ID already existing for that combination of State Code and County Code and Tribal Area.

Test Results

• Zero Span Value: A measurement obtained with gas from a zero concentration. Zero span is the observed value read from the instrument when the concentration of the specific parameter used to test the monitor was zero.
• Levels 1-5--Actual Value: For precision and accuracy data the actual value is the concentration produced from the primary sampler (i.e., routine monitor) in a collocated sampler pair.
• Levels 1-5--Indicated Value: The measurement recorded by a monitor for a standard gaseous concentration with which it has been challenged.