1 Dec. 11, 1997 LEADS Quality Control Systems Robert Brewer (512) Monitoring Operations Division Network QA Manager

2 Dec. 11, 1997 Quality Control (QC) Quality Control is the overall system of technical activities that measure the attributes and performance of a process, item, or service against defined standards to verify that they meet the stated requirements established by the customer.

3 Dec. 11, 1997 LEADS QC Checks n During Calibrations n Monitor Voltage and Concentration Outlier Checks n Concentration Spacing Check n Slope/Intercept Checks - Cal. only n Zero/Span Checks n Precision/Linearity Check - Cal. Only n Converter Efficiency Checks (NOx & H2S) n During Span Checks n Monitor Voltage and Concentration Outlier Checks n Concentration Spacing Check n Zero/Span Checks n Linearity Check - Span Only n Converter Efficiency Checks (NOx & H2S) n Span Source Audit - Checks the accuracy of the DASIBI 5008 Calibrator every 45 days

4 Dec. 11, 1997 Calibration Sequences n Sequences are composed of Levels. n Levels - A Level consists of a set concentration from the DASIBI 5008 calibrator introduced into a monitor for a set number of 5-min average updates. Each Level is assigned a letter code (M, R, S, T, or G) by the datalogger. n Updates - A set number of 5-min updates (usually 3) in each level are allowed for instrument stabilization. The remaining updates (usually 4) are processed by LEADS.

5 Dec. 11, 1997 O3, SO2, & CO Cal. Sequence Level M* R S T* G* Conc. (ppm) 0.4, CO , CO , CO , CO * Note - Levels used during Span Checks

6 Dec. 11, 1997 NO, NO2, & NOx Cal. Sequence NO2 Conc. (ppm) NOx Conc. (ppm) Level G* M* M†* R R† S S† T* T†* NO Conc. (ppm) *Note - Levels used during Span Checks †Note - Gas Phase Titration Levels

7 Dec. 11, 1997 Scrubber Bypassed NO Yes NO H2S Cal. Sequence SO2 Conc. (ppm) Level M* R S T* T1* T2* G* H2S Conc. (ppm) *Note - Levels used during Span Checks T1 - H2S Converter Efficiency Check T2 - SO2 Scrubber Efficiency Check

8 Dec. 11, 1997 Outlier Tests Min Updates StabilizationProcessed Updates Average of 4 Limits Voltage or Conc. Next Level Outlier is found so test is repeated without outlier.

9 Dec. 11, 1997 Outlier Tests - Second Pass Min Updates StabilizationProcessed Updates Average of 3 Limits Voltage or Conc. Next Level The first outlier is ignored. Remaining 3 updates are within limits. Result: Pass with Warning

10 Dec. 11, 1997 Concentration Spacing Test Voltage Concentration G T S R M - Warning or Failure Limit around Ideal Value Outside of Limit

11 Dec. 11, 1997 Slope and Intercept Tests (Cal. Only) Voltage Concentration G T S R M Slope Outside of Limit Intercept ²y ²x Slope = ²y ²x Intercept Limits Slope Limits Ideal Slope Note: Both Warning and Failure Limits are used in these tests. Regression Line

12 Dec. 11, 1997 Zero and Span Tests Voltage Concentration G T S R M Zero Limits Previous Cal. Span Voltage Previous Cal. Zero Voltage Span Limits Zero Voltage Out of Limits - Ideal Values Note: Both Warning and Failure Limits are used in these tests.

13 Dec. 11, 1997 Precision/Linearity Test (Cal. Only) Voltage Concentration G T S R M Note: Both Warning and Failure Limits are used in this test. Limits Regression Line Out of Limits

14 Dec. 11, 1997 Linearity Test (Span Check Only) Voltage Concentration G T S R M Note: Both Warning and Failure Limits are used in this test. Limits Line between Zero and Span Out of Limits

15 Dec. 11, 1997 NO2 Converter Efficiency Test n The NO2 Converter Efficiency is calculated for the M, R, S, and T concentration levels and compared to an ideal of 100%. n Efficiency is calculated from the change in response of the NOx channel when a level of nitric oxide is titrated with ozone to produce NO2. n Both Warning and Failure Limits are used in these tests.

16 Dec. 11, 1997 H2S Converter and Scrubber Efficiency Tests n H2S Converter and Scrubber Efficiency are calculated for the T level only and compared to an ideal of 100%. n Converter Efficiency is calculated from the monitor’s response to the T level of H2S (T) as compared to the T Level of SO2 with the scrubber bypassed (T1). n Scrubber Efficiency is calculated from the monitor’s response to the T level of SO2 with the scrubber bypassed (T1) as compared to the T Level of SO2 through the scrubber (T2). n Both Warning and Failure Limits are used in these tests.

17 Dec. 11, 1997 Ideal Values n Ideal values for each of the tests are listed in the Calibration and Span Check reports available from the LEADS Network Status Report Web Pages. n For Each Test, the Ideal Value is subtracted from the Measured Value to obtain the test error. This error is then compared to the Warning and Failure Limits.

18 Dec. 11, 1997 Test Limits n All QC tests performed on LEADS calibration or Span Check data have both Warning and Failure Limits except the Outlier Tests. Each Outlier Test uses only one Limit but the test is repeated once if an outlier is detected. n Each Warning Limit is chosen statistically to represent the 3 standard deviation value about the mean error of a test. This means that there should be only a 0.27% probability of exceeding a warning limit if the monitoring system is working properly. DO NOT IGNORE WARNINGS. n Each Failure Limit is chosen to be at least 1.5 times the warning limit and is intended to represent the maximum error that will be tolerated without invalidation of the affected data.

19 Dec. 11, 1997 Automatic Data Validation Rules n Automatic invalidation of data is based only on whether a QC test passes or fails. Warnings are not considered in this processing. n Failure of a Concentration Outlier test or a Concentration Spacing test indicates a problem with the calibration system but not with the monitor (except NO2). The Calibration or Span Check event involved is considered invalid and the ambient pollution data is unaffected. n Calibration QC Tests n Failure of a Monitor Outlier Test, Precision/Linearity Test, Converter Efficiency or Scrubber Efficiency Test causes invalidation of ambient data back to the last good Cal. or Span Check and forward to the next good Cal. n Failure of a Slope or Intercept Test causes ambient data invalidation forward to the next good Cal. n Failure of a Zero or Span test causes ambient data invalidation back to the last good Cal. or Span Check.

20 Dec. 11, 1997 Automatic Data Validation Rules (Cont.) n Span Check Tests n Failure of any test, except the Conc. Outlier and Spacing Tests, causes invalidation of ambient data back to the last good Cal. or Span Check and forward to the next good Cal.

21 Dec. 11, 1997 Span Source Audits QC n Span Source Audits evaluate the accuracy of the CAMS DASIBI 5008 calibrator. Corrective action is required if audit limits are exceeded. n If the audit passes, then the pollutant monitor must be adjusted to agree with the M-Level concentration produced by the CAMS DASIBI calibrator. This sets the Slope of the monitor’s calibration curve to the ideal. n If a Slope Test warning is reported thereafter, then action must be taken to determine if the error was caused by monitor drift or span source drift. A Span Source Audit may be needed if there are no obvious instrument problems.