The CEMS Hub is a centralized knowledge area focused on real-world operation of Continuous Emission Monitoring Systems in power plants, refineries, cement plants, steel plants, and industrial facilities.
This section is written from a field technician’s perspective, addressing compliance requirements, analyzer reliability, data quality, and common failure modes.
CEMS System Overview
- Gas analyzers (SO₂, NOx, CO, CO₂, O₂, HCl, HF)
- Sample probes and heated sample lines
- Sample conditioning systems
- Flow control, pumps, chillers, and filters
- Calibration systems (zero & span)
- Data Acquisition & Handling Systems (DAHS)
Common CEMS Analyzer Types
Gas Analyzers
SO₂, NOx, CO, CO₂, O₂ — NDIR, UV, chemiluminescence, zirconia.
Flow Measurement
Pitot, ultrasonic, thermal mass for stack gas flow.
Opacity / Dust
Transmissometer and scatter-based particulate monitoring.
Moisture
Wet/dry basis correction using moisture analyzers.
Common CEMS Issues (Field Reality)
- Frequent calibration failures
- Condensation and water carryover
- Sample line plugging or corrosion
- Analyzer drift and data validity flags
- DAHS communication and data gaps
Compliance & Regulatory Focus
- US EPA (40 CFR Part 60 / 75)
- EU Industrial Emissions Directive (IED)
- ISO 14181 (QAL1 / QAL2 / QAL3)
- Local environmental authority requirements
CEMS Best Practices
- Maintain consistent sample temperature above dew point
- Verify analyzer zero/span trends weekly
- Inspect probes and filters routinely
- Correlate analyzer data with process conditions
- Document all maintenance and calibration activities