What a CEMS measures
A continuous emission monitoring system measures pollutants in stack gas around the clock. Depending on the industry and consent conditions, typical parameters are:
- particulate matter (dust),
- gases such as SO2, NOx, CO, and in some processes HCl, HF or NH3,
- reference values such as O2, moisture, temperature and pressure,
- stack gas flow, needed to calculate mass emissions.
Why Indian plants need it
The Central Pollution Control Board directed the highly polluting industry categories to install online continuous emission and effluent monitoring and connect it to the CPCB and State Pollution Control Board servers. The exact parameters, data requirements and calibration practice come from the plant's consent and the applicable guidelines, so confirm them with your SPCB before specifying a system.
Gas analysers: extractive vs in-situ
| Extractive | In-situ | |
|---|---|---|
| How it works | A heated probe and line draw a sample to an analyser cabinet | The analyser measures directly across or inside the stack |
| Strengths | Many components in one system, easy access for maintenance and calibration | Fast response, no sample handling, fewer moving parts |
| Watch-outs | Sample conditioning must avoid condensation and losses | Installation and alignment on the stack; access at height |
| Examples | SICK MCS100E HW, GMS800 | SICK GM32, GM35 |
Dust monitoring
Dust monitors use optical methods such as scattered light or transmission. Scattered-light instruments suit low dust concentrations after efficient filters or ESPs; transmissometers suit higher concentrations. SICK's DUSTHUNTER family covers both, and dust monitors are normally correlated with gravimetric measurements made on the stack.
Stack flow measurement
Ultrasonic cross-stack flow meters such as SICK FLOWSIC100 measure the average gas velocity across the stack, which avoids the errors of single-point measurement in disturbed flow profiles.
Planning a reliable system
- Choose the sampling location with enough straight stack upstream and downstream, and safe platform access.
- Match analyser ranges to the actual emission levels and limits.
- Plan calibration gases, zero/span checks and periodic audits.
- Budget for preventive maintenance — filters, probes and pumps need regular attention.
Frequently asked questions
Can one system serve several stacks?
Some extractive systems switch between sampling points, but data requirements usually favour dedicated measurement per stack; check your consent conditions.
Who maintains the CEMS?
EECG supports commissioning, calibration and AMC so the system keeps reporting reliable data.
Browse SICK products at EECG
EECG is an authorised channel partner for SICK in Central India, with supply, installation and service support from our Raipur team.
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