Introduction to Quality Assurance of Continuous Emissions Monitoring

Large industrial plants are required to have and maintain an efficient process of Continuous Emissions Monitoring. In order to indicate that their processes are effective, and their emission monitoring systems meet the required criteria, there are carefully drafted EN Standards for assuring the high quality of permanently installed automated monitoring systems (AMS). In this article we will discuss the four stages of BS EN 14181 (2014): QAL1, QAL2, QAL3 and AST (Annual Surveillance Test).

Quality Assurance of CEMS ensures safety and clean emissions

In the previous blog article, we discussed the basics of emission monitoring in industrial settings, and what’s included in the monitoring process. In this article we will take a peek inside the industrial plants themselves, as we discuss the quality assurance of automated measuring systems. In other words, we will focus on the EN 14181 standard, which was first introduced in 2004 and updated again in 2014 to ensure that large combustion plants and waste incineration meet the required criteria demanded by law. In essence, EN 14181 sets the quality criteria for permanently installed measuring equipment at industrial plants.

The quality assurance of Continuous Emissions Monitoring Systems (CEMS) is divided into four Quality Assurance Levels: QAL1, QAL2, QAL3 and AST.

Let’s take a closer look at each level:

QAL1 – Quality Assurance Level 1 – Measuring Procedure Check

QAL1 – requires that instruments are shown to be suitable for purpose based upon a set of laboratory and field procedures, as set out in the EU Standard EN 15267. Testing must be carried out by an approved laboratory accredited to EN ISO/IEC 17025 (such as TUV or SIRA / CSA) by a national body.

QAL1 aims to find out whether the selected measuring equipment for a plant is effective enough and meets not only the required legal criteria, but also the needs of an industry operator. This includes the analyzer system itself (such as an FTIR), as well as the sample delivery and sample conditioning system (sample probe, sample lines etc.), so it is an assessment of a complete measuring system.

QAL1 certificate is like the driving license of a measuring system: once a system has been proven to be acceptable, it is granted a QAL1 certificate by SIRA (for MCERTS in the UK) and / or UBA/TÜV based on who carried out the performance trials, for the system that has undergone the laboratory and field performance trials. Parts that make up the certified measuring system are stated within the QAL certificate and or MCERTS Certificate.

The scope of the QAL1 certification is also expressed. For example, below is a typical statement taken from an MCERTS certificate that defines the scope and or limitations of the QAL certification.

“On the basis of the assessment and the ranges required for compliance with EU Directives this instrument is considered suitable for use on waste incineration and large coal-fired combustion plant applications. This CEM has been proven suitable for its measuring task (parameter and composition of the flue gas) by use of the QAL1 procedure specified in EN14181, for IED Chapter III and IED Chapter IV applications for the ranges specified. The lowest certified range for each determinand shall not be more than 1.5X the daily average emission limit value (ELV) for IED Chapter IV applications, and not more than 2.5X the ELV for IED Chapter III and other types of application”.

When assessing a QAL certificate, one key parameter you need to consider are the certified ranges of the system in question, compared against the daily emission limit value (ELV) of the intended application. Just because a system has a QAL1, it does not mean it is suitable for the process in mind.

QAL2 – Quality Assurance Level 2 – Installation

If QAL1 is the driving license, QAL2 could be seen as the regular inspection of a vehicle. The requirements of QAL2 cover the calibration of the CEMS / AMS against nationally approved analytical methods applied by a test organization accredited to EN ISO/IEC 17025 (and MCERTS in the UK) by a national body.

This stage of quality assurance specifies the procedures to ensure that the continuous emissions monitoring system has been correctly installed, calibrated by comparison measurement and independently verified.

The QAL2 procedure comprises of the following:

  1. Installation of the AMS
  2. Functional test(s) of the AMS
  3. Parallel measurements with the SRM for each parameter (as defined in the sites Environmental Permit)
  4. Data evaluation
  5. Calculation of variability of the AMS measured values
  6. Test of variability of the AMS measured values and validity of the calibration function
  7. Reporting
  8. Inputting QAL2 Calibration Factor(s)

According to EN14181, points 3, 4, 5, 6 & 7 are typically carried out by an accredited laboratory. The laboratory performing the measurements with the SRM shall be accredited for this task according to EN ISO/IEC 17025, or shall be approved directly by the relevant competent authority. This is to ensure that the assessment is independent of the manufacturer / supplier, so that the end user can be assured as to whether the system meets QAL2 or not.

Typically, QAL2 tests are carried out in every 5 years (as defined in the site’s environmental permit). It is, however, important to point out that if there are any major changes made to the plant or process being measured that might affect the emissions (both positively and negatively) or the ability of the CEMS to measure a parameter, an operator must have the AMS evaluated and conduct another QAL2 assessment. A major change could mean, for example, a change in the fuel types, an alteration to combustion or incarceration processes, or anything that might radically change the emissions.


QAL3 – Quality Assurance Level 3 – Ongoing Monitoring 

QAL3 refers to the ongoing monitoring of a CEMS between the QAL2 tests. Operators are required to keep an eye on the stability and performance of their monitoring systems.

EN 14181 recommends that plant operators start collecting data for QAL3 immediately after the CEMS has been installed and commissioned. This ensures that there is enough reported information of the performance and functionality of the monitoring system and helps reduce the chances of the measurement system not meeting the requirements as set out in QAL2. This bedding in period is typically around 3 months, though on very stable processes with good performing systems, this period is often reduced.

With QAL3 monitoring, industrial plants are able to spot any drifts in the zero/span levels and point out if the system has any needs for maintenance.

AST – Annual Surveillance Test

Annual Surveillance Tests are very similar to QAL2 test but are carried out in a smaller scale. These mini-QAL2 tests are functional laboratory spot tests that map out the performance of a CEMS.

Their purpose is to verify the continuing validity of the calibration function, and the requirements and responsibilities for carrying out the AST tests are the same as for QAL2.

AST covers the following items:

  1. functional test of the AMS
  2. parallel measurements with the SRM
  3. data evaluation
  4. calculation of variability of the AMS measured values
  5. test of variability of the AMS measured values and validity of the calibration function
  6. reporting

Note 1: Points 2, 3, 4, 5 & 6 are typically carried out by an accredited laboratory. The laboratory performing the measurements with the SRM shall be accredited for this task according to EN ISO/IEC 17025, or shall be approved directly by the relevant competent authority. This is to ensure that the assessment is independent of the manufacturer / supplier, so that the end user can be assured as to whether the system meets the requirements set out in EN14181 for Annual Surveillance Tests.

Note 2: If the AMS fails to meet the performance requirements outlined within EN14181 for the Annual Surveillance Test, then a full QAL2 must be undertaken again unless otherwise instructed by the local regulator authority issuing the sites permit.

Roles and Responsibilities in Continuous Emissions Monitoring Quality Assurance

Industrial plant operators are responsible for their emission monitoring systems’ good functionality and condition. Furthermore, it is their duty to liaise with the authorities and to provide them with all the required documentation.

As QAL1, QAL2, AST and QAL3 require seamless co-operation of a number of different parties, it might be beneficial to clarify the roles and duties of each stakeholder in the processes:

Suppliers and Manufacturers of CEMS

  • QAL1 certificates for CEMS
  • Appropriate and safe installing of a CEMS
  • Co-operation with the plant operator before QAL2 and AST tests (and during, if necessary)

Test Laboratories:

  • Maintenance of accredited Standard Reference Methods for QAL2 and ASTs.
  • Functional tests (QAL2 and AST): sampling or auditing the test results by other parties

Note 3: Functional tests can be carried out by the manufacturer / supplier / System integrator. It is the responsibility of the Test Laboratory to ensure that such tests are carried out correctly.

Industrial Plants / Process Operators:

  • QAL2, QAL3 & AST reporting to regulators and local authorities
  • Performing QAL3

Regulators / Local Emission Authorities

  • Assessing operator compliance
  • Assessing test laboratories
  • Providing guidance on EN 14181

Interpreting the Directives and laws for continuous emissions monitoring is often a complex procedure and requires close-knit co-operation of a wide range of operators and stakeholders. The principle behind of it all is, however, to ensure better safety and a clear framework for emissions monitoring. With the common EN 14181 framework we can be sure that industrial plants are doing their job and are looking after their emissions and air quality for us all.

Gasmet contributes to the quality assurance too, as our CMM AutoQAL, CMM and CEMS solutions are QAL1 certified by TÜV and MCERTS.


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