The Acid Rain Program experience has shown that continuous emissions monitor (CEMS) operators can eliminate bias from monitoring systems by instituting appropriate installation, operation, and quality assurance procedures. The “An Operator’s Guide to Eliminating Bias in CEM Systems” on this page provides information recognizing the physical and operational problems that produce systematic error and their available remedies.
The Guide makes it easier for CEMS operators to improve a monitor's accuracy and meet regulatory requirements. We recommend viewing the entire individual chapters.
- Chapter 1 describes the history and the engineering and statistical basis for the bias test.
- Chapters 2 through 7 describe problems that can cause systematic measurement error and remedies that can be taken to address those problems. Each chapter includes a table summarizing the problems discussed in that chapter.
- The Checklist provides a cross-reference of all the problems discussed in these chapters.
- Chapter 8 discusses elements that should be incorporated into ongoing quality assurance programs to detect and prevent the problems that produce systematic error in monitor measurements.
For more emissions monitoring resources, return to Emissions Monitoring and Reporting.You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.
- An Operator's Guide To Eliminating Bias In CEM Systems (PDF)(122 pp, 1 MB, November 1994)
- Introduction and Table of Contents (PDF)(11 pp, 76 K, November 1994)
- Chapter 1: Overview: Accuracy, Precision, and Bias in Continuous Emission Monitoring Systems (PDF)(12 pp, 111 K, November 1994)
- Chapter 2: Bias Due to Probe Location and Stratification (PDF)(14 pp, 163 K, November 1994)
- Chapter 3: Sources of Bias in Extractive CEM Systems (PDF)(15 pp, 140 K, November 1994)
- Chapter 4: Sources of Bias in In-Situ Monitoring Systems (PDF)(13 pp, 243 K, November 1994)
- Chapter 5: Sources of Bias in Flow Monitoring Systems (PDF)(8 pp, 78 K, November 1994)
- Chapter 6: Sources of Bias in the Gas Analyzer (PDF)(15 pp, 111 K, November 1994)
- Chapter 7: Sources of Bias in the Data Acquisition and Handling System (PDF)(10 pp, 63 K, November 1994)
- Poster: Eliminating Bias in CEM Systems - A Checklist (PDF)(9 pp, 96 K, November 1994)
- Chapter 8: Bias and Quality Assurance Programs (PDF)(15 pp, 118 K, November 1994)