- Model QAL 991 - Particulate Continuous Emission Monitor



The PCME QAL 991 is an approved Particulate CEM (Continuous Emission Monitor) designed to meet and exceed CEN standard EN 14181 / EN 13284-2. Particularly suited to monitoring emissions from industrial processes regulated under the European Waste Incineration Directive (WID) and Large Combustion Power Plant Directive (LCPD), the PCME QAL 991 is also proven in other industrial processes controlled with high efficiency bag filtration. The instrument holds QAL1 approval specified in EN 15267-3, under both MCERTS and TUV.

ENVEA UK's patented ElectroDynamic Probe Electrification technology extracts a specific frequency band from the induced AC current signature and filters out the DC current caused by particle collisions. The technology outperforms conventional DC triboelectric systems and alternative AC systems by extending the velocity range over which the instrument has no cross sensitivity to changing velocity, and is unaffected by contamination of the sensor rod, eliminating concerns of signal drift.

  • System self-checks, with logging of Zero and Span check data for QAL3 reporting and probe rod short circuit check to detect (hence avoid) electrical shorting to the stack
  • QAL Reporter PC software option to provide secure and powerful emissions reporting and automated QAL3 reporting in full compliance with EN 13284-2
  • Entry and Standard control units with advanced graphics and user interface screens, features including alarming, graphical trending, data logging, 4-20mA output.
  • PLUS control unit option for sensor networking (up to 16 sensor channels) via industry standard Modbus, multiple inputs for external devices (e.g. for Temp and O2 normalisation)

The PCME QAL 991 supersedes the DT991, an instrument proven in demanding CEM applications worldwide.

Audit Tools & QAL3 Reporting

As an approved Particulate Measurement System for compliance monitoring, the PCME QAL 991 has fully automated self checks (Zero and Span) with a dedicated audit channel for QA data logging. This enables a simplified process for operators to meet QAL3 standards, with the option of PCME’s QAL Reporter PC software for automated QAL3 reporting in full compliance EN 13284-2.

In addition to automatic self checks, the PCME QAL 991 offers a manual audit unit providing ultimate quality assurance, enabling a further layer of auditing for measurement and system integrity. The ElectroDynamic™ 5-point audit unit facilitates a comprehensive system check via a 5 point linearity check.

Extended Velocity Range

The PCME QAL 991 uses unique ElectroDynamic Probe Electrification technology, which outperforms alternative probe electrification technologies by extracting a specific frequency band of the induced AC signal. This patented feature ensures confidence in accurate and representative data by eliminating any cross-sensitivity to changing flue gas velocity within typical bagfilter velocity ranges (8-20m/s) whilst maintaining stable, high resolution sensing characteristics.

Probe Contamination Tolerance

Different probe based sensing technologies having variable tolerance to probe rod contamination from particulate matter. The PCME QAL 991 with ElectroDynamic Probe Electrification technology overcomes these limitations:

  • Electronically rejects DC signal and filters AC signal, eliminating signal drift concerns associated with DC Triboelectric and combination AC/DC technologies caused by accumulation of particulate matter on probe
  • Passive section on probe rod prevents short circuit to stack wall, by creating clearance between active section of sensor and potential contamination ‘bridging’ sites near connection stub
  • No air purge required for rod, insulator air purge only recommended with conductive particulates

Process Conditions

The PCME QAL 991 is suitable for:

  • Industrial processes controlled with dry scrubbing and high efficiency bag filtration
  • Non-condensing / dry flue gases*
  • Constant or variable velocities within range 8-20m/s (typical bagfilter velocity ranges), constant velocity required outside this range
  • Not suitable for electrostatic precipitators or applications with water droplets*

* For wet / condensing flue gas applications see PCME STACK 181 WS

Typical Applications

The PCME QAL 991 is used to monitor emissions from processes regulated under the European Waste Incineration Directive (WID) and Large Combustion Plant Directive (LCPD) eg:

  • Coal fired power stations / Coal Mills
  • Gas/Oil fired power stations
  • Gas turbines
  • HEPA filter plant
  • Biomass power plant
  • Municipal Incineration
  • Cement Kiln


  • Approvals: QAL1 approved to EN 15267-3 (for EN 14181, EN ISO 14956) under MCERTS (Performance Standards for CEMs version 3, class 1) and TUV (BlmSch 17, 13, 27: latest revision
  • more on approvals
  • Certification Range: 0-15 mg/m3
  • Measurement Capability: 0-100 mg/m3
  • Long Term Zero Drift: < 0.1 mg/m3
  • Air Purge Requirement: May be required on some applications (consult PCME), 5-10 litres/min of dry, clean, oil free instrument air
  • Inspection Frequency: 6 months (dependant on application)
  • Stack Diameters: 500mm – 3m (multi-sensor configuration required for stack >3m)
  • Stack Temperatures: 0-250°C


  • 316 Stainless Steel, 0-250°C
  • Standard or with Passive section (for short circuit prevention by creating clearance between active section of sensor and potential contamination 'bridging' sites)
  • RS485 (Mobus) output to Controller
  • 24VDC power supplied via Controller
  • IP65 die-cast aluminium enclosure
  • External Audit Unit for 5-point linearity check

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