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Summary of updates

Protocols and performance specifications page
Summary
Number Section Summary of updates to 2005 PG/7 version
1 1. Introduction Applicable to monitoring emissions of SO2, NOx and CO2 from large combustion sources, which may be extended to other contaminants and point sources.
2 2. Summary of specifications and protocols Specifications and protocols are presented in narrative detail, as well as in summary tables that may serve as a quick reference to those familiar with the subject (for example, Tables 3, 6 and 7).
3 3.1.1 Location of the calibration gas injection port All CEMS installed after 2025 must be able to conduct the daily calibration drift and the quarterly linearity tests using as reference flowing calibration gases.
4 3.2.1 Operating range The initially proposed Full Scale (FS) rule based on most of the CEMS measurement to be within 20% and 80% of the FS (as per US 40 CFR part 75) was abandoned due to consistent adverse stakeholder comments. In this updated draft, it is the appropriate regulatory authority that approves the FS of the CEMS so that they are adequate to the purpose of the monitoring and the emission pattern of the source. As a general principle the FS of the analyzers should encompass all expected stack gas levels.
5 3.2.2 Interference and 3.2.3 Temperature-response drift The analyzer manufacturer must certify that the sum of combustion exhaust interferences is ≤ 4.0% of FS, as well as meeting certain temperature response drift specifications.
6 3.2.4. NOx converters If NOx analyzers rely on NO2 converters then the efficiency must be tested semi-annually, as per defined protocols.
7 3.2.5 FTIR extractive CEMS An FTIR analyzer may be used as a CEMS component to monitor NOx, SO2, CO and CO2 concentrations of the exhaust gases of a combustion source, providing that the FTIR met the applicable analyzer specifications of this document, including the required daily, quarterly, annual or semi-annual QA/QC tests.
8 3.4 DAHS specifications Defines enhanced capabilities to compile monthly CEMS reports, and annual third-party audit. DAHS must archive monthly and annual hourly data, including availability, certification tests, CGA, RATA, BAF, and backfilling.
9 3.4.1 Backfilling of missing data Examples of backfilling options are presented. Specifics must be described in the Quality Assurance Plan (QAP) and be accepted by the appropriate regulatory authority.
10 3.5 Time-shared systems After 2025, new time-shared CEMS will be limited to 2 adjacent sources.
11 3.6 Test procedures for verification of design specifications Analyzer interference rejection, temperature response to be tested by the CEMS manufacturer, with certificate of conformance archived in the QAP manual.
12 4.2 Representativeness EPA Methods 2G (2 dimensional probes) or 2F (3 dimensional probes) may be used as flow reference methods for certification and subsequent RATA when cyclonic flow cannot be otherwise corrected.
13 Table 3, page 16 PG7 2005 Section 5.3.4.6 note that allows (for gas concentrations ≤ 250 ppm) the substitution of RM Avg. for FS in the RA calculation was deleted. The ± 8 ppm alternate RA for NOx was maintained. Limited bias to ≤ 5.0% FS (or alternate limits) for all contaminants, diluents and flow.
14 5.3.2, and 5.3.3 Calibration drift and linearity check protocols Narrative for calibration drift protocol (7 days, 2 level test per day) was separated from the linearity CGA protocol (3 runs, 3 levels per run). Both these tests may be performed during the Operation Test Period (OTP).
15 5.3.6 Bias test calculations Bias ≤± 5.0 %FS are acceptable, with low level source alternative limits. If there is Bias a set of CEMS measurements, and the average RM measurements are ≥ 30% FS, then the subsequent measurements must be corrected by a Bias Adjustment Factor (BAF) that compensate for the bias. Else no BAF should apply.
16 6.3.1.6 Alternate quarterly analyzer audit Deleted former method EPS 1/RM/15 reference to perform alternate quarterly audits to CEMS installed before 2025 that cannot be calibrated with flowing gases. Replaced by abbreviated RATA using portable analyzer that meets RM specifications including Protocol gas calibration. Alternate acceptable RA ≤ 15% for pollutants and diluents, or 1.0% absolute difference for O2 and CO2.
17 6.4.2 Exemptions from semi-annual performance evaluations

The semi-annual tests may be waived and conducted annually if all the following conditions have been met, providing that the CEMS includes the monitored parameter:

  • the system availability is greater than 90% annually
  • the CGA tests are conducted with flowing test gases
  • the previous 2 RATA evaluations were passed on the first attempt (by ≤ 10.0% RA or by the alternate limit)
  • sources that operate less than 1500 hours per year are waived from semi-annual evaluations (in these sources RATA must be performed every 2 years)
18 Table 6, page 34, Daily and quarterly performance evaluations summary Removed the redundant daily drift limit for dry O2 - wet O2 moisture monitors (but maintained drift limit for O2 and CO2 analyzers). Linearity CGA limits relative to FS for SO2, NOx and CO, whereas for O2 and CO2 are ≤± 0.5% O2 or CO2 respectively. Includes an "Alternate CGA" audit for already installed CEMS that cannot perform CGA with flowing gases.
19 6.5.2 Independent inspection Summarized the minimum scope of the annual 3rd party inspection of the CEMS QA/QC, based on the review of the QAP and the DAHS data: hours of quality assured data; out-of-control hours; backfilled hours; in addition to the results of quarterly, semi-annual or annual performance tests (CGAs, flow checks, and RATAs). Narrative discussion of non-compliance issues, corrective actions to out-of-control occurrences and recommendations to improve CEMS performance.
20 Table 7, page 38, Semi-annual or annual performance evaluations summary Set the RA alternate SO2 error limit at ± 15 ppm SO2 and the corresponding value for NOx was maintained at ± 8 ppm. Bias was limited to ≤± 5.0% FS for contaminants, diluents, temperature and flow. Included an alternate error limit for stack gas moisture and temperature. Removed the calculated mass emission RA specifications, due to redundancy and potential discrepancy with CEMS measurement specifications.
21 7. Determination of carbon dioxide emissions This section provides for estimation of CO2 in combustion exhaust gas by monitoring the exhaust gas O2 level or CO2 level on a wet and dry basis.
22 Glossary, page 42 New peaking unit definition: combustion unit operated ≤ 1500 hours within a calendar year. Various waivers applicable to these units are included in sections 5.1.1, 5.1.3, 6.3.1, 6.3.3, and 6.5.1
23 Appendix A, Emission calculation by combustion "F" factors Applicable to combustion sources CEMS where the desired result is emission per heat input (no flow monitor). The updated Appendix A expands the previous F-Factors table; corrects a formula error (Kx values); and prescribe remedies for transition periods of extreme high O2 or low CO2.
24 Appendix B, Determination of mass emission rate Minor editing to this Appendix, except for the addition of linear equations to calculate combustion stack gas moisture from measured O2 wet (for NG, Oil and Coal), and average monthly air moisture on Canadian provincial capitals, which combined may result in acceptable stack gas moisture levels.
25 Appendix C, Relative accuracy and bias example calculations Example calculations of relative accuracy, bias, and BAF for SO2, NOx, stack gas flow, O2, CO2, moisture and stack gas temperature, were included with the corresponding spreadsheet functions and the applicable PG/7 specifications. Additionally, there is an example of the Grubbs test to eliminate RATA outliers.

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