Background
The U.S.EPA requires that each and every analyzer installed as a CEMS ("continuous emissions monitoring system" for compliance monitoring and reporting) must be tested following installation [Certification Test] to verify compliance with the applicable Federal Standards and Regulations, which includes, but is not limited to 40 CFR Part 60, Appendix B [Instrument Performance Specifications]; 40 CFR Part 60, Appendix F [Quality Assurance Procedures]; and/or 40 CFR Part 75 [Continuous Emission Monitoring], the "Acid Rain" rules. In addition, performance specs require that the equipment’s zero and span drift must be checked daily to verify that it continues to operate within specifications.

Explanation
The EPA does not issue a "blanket" approval of an analyzer Model type for continuous flue gas emissions monitoring; but rather, each and every installation must be individually tested, on site, in the specific application and environment, to verify compliance, and the installation must be retested annually, for its lifetime, to verify continued compliance.

Initial CEMS Certification Test: Generally the plant will arrange for the test, and will coordinate with a similar set of tests on the combustion source as well as the control hardware (but sometimes the plant will also contract the CEMS testing with the CEMS supplier). An independent third-party testing company will bring their equipment to the site and will perform a series of EPA reference tests on the flue gas emissions, for a minimum of 9 tests (for instrument certification). The average of these tests is compared with the average a report for the plant to submit to the regional EPA office. Examples of such test reports are available upon request.

Approval
The resulting EPA approval is an approval to the plant that they can operate their facility, as long as the tested CEMS continues to operate properly [within specifications, i.e. daily drifts; % data collection (under Part 75); quarterly relative accuracy {RA} checks (under Part 60 App F); etc]. If the equipment does not meet the specs, it must be repaired, retested, and pass; or it must be replaced with another system that does pass.

Approved Installations Equipped with AIM Analyzers
There are many approved installations equipped with AIM analyzers, both the in-situ as well as the extractive Model .... and probably more importantly, no installations where AIM has failed the test and been replaced with another analyzer. AIM EPA Compliance installations have included municipal waste incinerators, hazardous waste incinerators, hospital waste incinerators, fluidized bed boilers and incinerators, industrial boilers and utility boilers; measuring Opacity, O2, CO, CO2, NOx, NO, NO2, SO2, THC, HCI, and H2O, with Data Acquisition & Reporting.

Daily Drift Checks
40 CFR Part 60, Appendix B requires each CEMS zero and span drift be checked daily. Both negative and positive drifts must be measurable. Zero is the instrument response with no sample, and span is typically 90% of range (with the range set at 150 to 250% of the emission limit). If out of spec, appropriate action must be taken [refer to AIM Field QC Program Manual, rear of the O&M Manual]. All AIM systems offer the ability for automatic calibration check and data logging. [One of the benefits of the in-situ Model E-6000 is that the accepted EPA daily drift checks do not require the use of calibration gases… a significant operating cost reduction. The system always includes an internal zero mirror and reference span filters which automatically sequence into the beam at a preprogrammed interval for the daily drift check. (EPA requires this check every 24 hours. Other agencies might require more frequent check; and some local agencies require the use of gases, either daily or monthly.)]

The drift is computed by the system controller, as the difference between the measured value and the initial value. This drift data is stored in memory, and can be accessed through the operator interface, and summarized in the optional DAS report.

NOTE In the US, the local agencies are allowed to required more stringent requirements than the EPA requirements, if they desire. In several regions, including So. California, as well as New England, New York, Now Jersey, and Pennsylvania the daily zero and span drift checks must be performed with cylinder gases. In this case, for the in-site systems, the optional internal audit cell [used for the quarterly relative accuracy audits] is used for the daily calibration checks also (see CGA below).

The extractive system [Model 5000, 7100, 7200, FTIR, etc] analyzers are calibrated in the classical way, either manually or automatically under the PC control. The calibration gas is inserted at the sample probe be opening a solenoid valve. The cal gas rather than sample flows through the system and through the sample cell.

Quarterly Relative Accuracy Checks [Cylinder Gas Audits, CGAs]: Reference standard [EPA Protocol] cylinder gases (typically located outdoors at ground level) flow through the in-situ internal audit cell and/or the extractive sample cell, for the quarterly cylinder gas audits. Mixed/blended gases can be used to reduce the calibration cycle time.