KPIs and measurements
Continuous Emissions Monitoring System
Also known as CEMS, continuous emissions monitor.
A Continuous Emissions Monitoring System (CEMS) is the suite of instruments that measures stack emissions in real time. A typical industrial CEMS measures opacity, particulate matter, NOx, SOx, CO, O₂, moisture and gas flow. CEMS data is the primary basis for environmental-compliance reporting under most jurisdictions' emission permits.
CEMS quality assurance
CEMS instruments are governed by quality-assurance frameworks:
- EU — EN 14181 (QAL1, QAL2, QAL3 and AST)
- US — EPA Reference Method 6, 7, 19 etc. plus Part 75 CEMS requirements
- National regulators — various local specifics
How cleaning intersects with CEMS data
Operators see fouling-driven degradation of ESP or baghouse performance in near-real-time on the CEMS trace. A rising opacity baseline, more frequent excursions, or trended particulate increase all indicate worsening collection. Active sonic-horn cleaning that defends collection efficiency shows up on CEMS as flatter, lower, more predictable traces.
Related terms
Related terms
- Opacity (stack)Opacity is the percentage of light obscured by particulate in stack flue gas. The headline visual KPI for ESP performance; continuously monitored and permit-limited.
- Particulate matterParticulate matter is regulated airborne particulate. PM10 = below 10 µm aerodynamic diameter; PM2.5 = below 2.5 µm; PM1 = below 1 µm. Smaller is more health-significant and harder to capture.
- NOx, SOx and CO emissionsNOx (nitrogen oxides), SOx (sulphur oxides) and CO (carbon monoxide) are the principal regulated gaseous emissions from combustion plants. Continuously measured by CEMS.
- EN 14181 and EN 13284EN 14181 sets European quality-assurance levels for stationary-source CEMS. EN 13284 covers manual reference methods for low-range particulate determination.