Continuous Emissions Monitoring Systems (CEMS) Solutions

What is CEMS (Continuous Emissions Monitoring Systems)?

Continuous Emissions Monitoring Systems (CEMS) measure a wide range of organic and inorganic gaseous air pollutants and particulates generated by specific industrial processes such as power plants, energy from waste plants and cement plants etc.  These pollutants are emitted directly into the atmosphere, typically via a tall stack where they become diluted and mixed into the ambient air. This can often contribute to additional air pollution at the local or even regional level, however in the UK, a long standing history of air pollution legislation and directives have seen phenomenal improvements in air quality, despite air poor air pollution being one of the biggest public health issues with >40,000 excess deaths per year in the UK alone.

Continuous Emissions Monitoring is a legal requirement in the UK. Site owners are required by law to ensure that appropriate mechanisms are in place for continuous emission monitoring, and must regularly check the equipment is functioning as it should be. It is also a legal requirement to store and analyse any data collected by the system.

CEMS (Continuous Emissions Monitoring Systems) are instrumentation systems designed to continuously collect and report data on the emission levels of pollutants from industrial sources. These systems are crucial for environmental compliance, allowing you to monitor and manage emissions in real time.

ET has been designing, installing, and supporting high quality Continuous Emissions Systems since 1983. Our mission remains unchanged – to provide you with high quality, highly reliable CEMS that require minimal maintenance and deliver maximum value.


We are proud to be the UK distributor for OPSIS CEMS, bringing you cutting-edge, optical, cross-duct, multi-gas measurement technology. OPSIS CEM Systems allow you to measure gases directly as they flow through the stack, all without any contact.

Versatile and adaptable, our OPSIS CEMS can be effortlessly customised for nearly any CEM and Process Control application.

OPSIS systems have an advantage over competitors as a single gas analyser is able to measure a wide-range of gaseous compounds, often in multiple gas ducts, which is a cost-efficient monitoring solution.

OPSIS system 400 – One system, three solutions

Key Benefits of OPSIS CEMS

OPSIS CEMS provide a range of benefits, including:

  • Cross Duct DOAS Technology: OPSIS CEMS use cross-duct Differential Optical Absorption Spectroscopy (DOAS) technology to give accurate and reliable measurements of various gases.
  • Optical multiplexing for cost savings: OPSIS CEM systems feature optical multiplexing capabilities, enabling cost savings by monitoring multiple processes and challenges simultaneously with a single system and without the complications of gas multiplexing.
  • In-Situ Measurements: One of its key features is the ability to take measurements directly at the source, eliminating the need for extracting and diluting flue gases. This is especially useful in situations where the flue gas is dusty, very humid, or aggressive.
  • MCERTS accredited :demonstrating compliance with industry standards
  • Space efficient: OPSIS CEMS require less space and have fewer working parts than other CEMS, eliminating the need for pumps and valves.
  • Energy efficient: OPSIS equipment consumes less energy, offering economic and environmental benefits, including a smaller carbon footprint, aligning with sustainability goals and Net Zero initiatives.
  • Low operating costs: lower maintenance, energy efficiency, and reduced downtime make OPSIS CEMS cost effective
  • Versatile: OPSIS CEMS can be applied to other applications such as dioxins sampling and mercury monitoring, expanding beyond emissions monitoring.
  • Expandable and Adaptable: OPSIS systems can easily accommodate additional gases for monitoring, making them expandable and adaptable to changing monitoring needs without requiring the purchase of a new analyser.

What to expect with ET CEM Solutions?

Site visit

A thorough site visit will allow us to determine suitable locations for your new CEM system and allows us to make sure the CEMS solution will meet your needs


After the site visit, our expert CEMS engineers will work together with you to develop a detailed specification. This involves assessing your emissions monitoring objectives, regulatory compliance requirements, and any specific industry standards applicable to your operations. 


ET’s experienced CEMS engineers will install your CEM system. Whether you are implementing a new system or upgrading an existing one, our installation process is conducted efficiently, minimising disruption to your operations.


Our engineers will test and validate the system to ensure that it functions following the specified requirements and industry standards. This phase includes the calibration of sensors, verification of data accuracy, and the establishment of communication links. The commissioning process concludes with a comprehensive review to confirm that your CEMS is fully operational and ready to provide accurate and reliable emissions data.


Get in touch

Please enable JavaScript in your browser to complete this form.