QAL Certification: QAL 1, QAL 2, QAL 3, Linearity and IAR

This series of field activities carried out by the professional team of the Tecnova HT Service Division is implemented following the publication of the new UNI EN 14181:2015 standard “Stationary source emissions – Quality assurance of automated measuring systems”, which replaces the previous UNI EN 14181:2004. It now represents the new benchmark for defining the levels of quality assurance (QAL) for Automated Measuring Systems (AMS) installed in industrial plants. In practice, it outlines all actions to be taken and documented to keep your CEMS compliant — and, crucially, to be able to demonstrate compliance to regulatory bodies.

It goes without saying that these activities must be carried out by any legitimate service team, and the time needed to perform them professionally is not compressible. Maintaining certified and calibrated instrumentation is also essential. Therefore, so called “qualified companies” offering the same services as the Tecnova HT Service Division with fewer site visits and significantly lower costs should be closely scrutinized by clients to avoid costly surprises during the next audit.

If the CEMS was engineered, integrated, and validated by Tecnova HT, the system’s compliance and quality control are already assured and traceable through the accompanying documentation. However, if the Tecnova HT Service Division is asked to work on CEMS from third party vendors, the following checks are performed:

• Sampling method and its effectiveness
• Characteristics of the analyzers used, particularly regarding QAL 1 certification from the manufacturer
• Description of the data acquisition, processing, and storage system

QAL 1 certification, issued by an accredited thirdparty body (e.g., TÜV in Germany), confirms the suitability of a specific analyzer to be used within a certified CEMS or as a standalone unit. If such certification is missing, the Tecnova HT Service Division can replace the noncompliant analyzer with a fully approved alternative. We always recommend clients verify that their analyzer is included in the official certified list, such as the one provided by TÜV (e.g., for FUJI Electric, refer to the link on the TÜV website).

Note that QAL 1 is a standardized evaluation of an instrument’s characteristics to assess its fitness for measuring tasks as defined in UNI EN 152673:2008. It is a necessary, though not sufficient, requirement for a fully compliant CEMS.

To help protect and maximize our clients’ investments and ensure full compliance with UNI EN 14181:2015, the Tecnova HT Service Division offers longterm onsite services that fulfill — and often exceed — all regulatory requirements. This includes Periodic Checks such as QAL 2 and AST, as well as specific tests like Linearity verification or IAR (Index of Relative Accuracy).

The same standard mandates that the testing methods used for verifying the CEMS must be recognized official methods, and the personnel conducting these reference measurements must be accredited under UNI CEI EN ISO/IEC 17025:2005 for each method used. These professionals belong to a Certified ThirdParty Laboratory appointed by the client and supervised by the Tecnova HT Service Division.

When is QAL 2 required?

If your CEMS adheres to UNI EN 14181:2015, QAL 2 verification must be completed within six months of issuing the CEMS Quality Management Manual (or its latest revision). This comprehensive system evaluation — including verification of the representativeness of the sampling point — is required at installation, at least every five years, or after any substantial changes to the plant or instrumentation.

QAL 2 involves:

• Verifying that analyzers are installed according to the supplier’s specifications (e.g., Tecnova HT)
• Confirming that CEMS data management processes are correct
• Defining normal operating conditions (e.g., technical minimums, operational hours)
• Determining calibration curves for each analyzer under actual operating conditions

What about AST – Annual Surveillance Test?

As per UNI EN 14181:2015, the AST checks the continued performance of your CEMS every 12 months using parallel measurements with reference methods. Its main goal is to confirm whether the QAL 2 calibration remains valid, using fewer data points (typically five). It is essentially a “lighter” version of QAL 2. Again, once commissioned by the client, the Tecnova HT Service Division supervises these tests performed by an Accredited ThirdParty Laboratory.

Linearity Tests

For additional field testing, the Tecnova HT Service Division can carry out gas analyzer linearity checks using scalar concentration cylinders or, preferably, its own certified diluter. These tests include a minimum of five measurement points within the analyser’s full range, with at least three repetitions per point. These guarantees clients are fully prepared for the next QAL 2 check.

IAR – Index of Accuracy Assessment

In plants where UNI EN 14181:2015 is not implemented, instrument calibration/verification is carried out for each parameter measured by the CEMS, either after gas extraction or in situ. For example, Tecnova HT evaluates measurement accuracy by calculating the Index of Relative Accuracy (IAR), comparing data collected at the same sampling point by both the CEMS under test and a certified reference method (SR). All data must:

• Be based on at least 15 samples, as required by the standard
• Reflect the same time base (e.g., hour or half hour) used to define the emission limit
• Be normalized to the same conditions (temperature, pressure, humidity) and match the CEMS operating state (“asis” data)

QAL 3 – Calibration Drift and Status Checks

The Tecnova HT Service Division also conducts QAL 3 checks to monitor the calibration status of CEMS and auxiliary measurements (e.g., temperature, pressure, humidity), typically on a weekly basis as defined in UNI EN 14181:2015. The goal is to ensure measurement precision and stability between two consecutive ASTs.

QAL 3 procedures “must demonstrate a periodic method capable of detecting potential anomalies in the system before they significantly compromise measurements.” In practice, this means that validated software used by Tecnova HT can assess analyzer drift and accuracy in realtime. For instance, if FUJI Electric recommends monthly calibration but weekly adjustments are needed, this indicates a hidden issue that must be promptly identified and addressed.

When you don’t know the details, it all seems overwhelming — but don’t worry.
Tecnova HT’s Service Division is your single point of contact to keep your CEMS in top shape.

QAL CERTIFICATION – Tecnova HT Service Division

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