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Do I Need CEMS? – Continuous Emissions Monitoring FAQ

7 April 2022

Do I need CEMS? Continuous emissions monitoring FAQ

Continuous emissions monitoring systems (CEMS) are used to monitor emissions to atmosphere from industrial installations. It is a legal requirement for many sites in the UK, who may be unsure of their obligations under environmental permits.

What are CEMS?

CEMS are used to monitor and record pollutants that are emitted to the atmosphere. Pollutants are typically created as a by-product of combustion or manufacturing processes. 

Typically, CEMS will either be extractive or in-situ.

Extractive CEMS transport a sample for measurement away from the point source. A typical extractive CEMS will comprise:

  • A sample probe – this will be heated if condensation is likely to be problematic
  • Filtration
  • Sample line – again, this will be heated if condensation is likely to be problematic
  • Gas conditioning – such as a cooler to rapidly remove moisture from the sample
  • An analyser

This all comes under sample preconditioning.

In-situ CEMS measure the sample at the point source, eliminating the requirement for sample pre-conditioning. A typical example of an in-situ CEMS is the Sintrol S305QAL dust probe.

Data acquisition software will be required to log and record data, enabling the site to provide emission reports to the governing body, such as the Environment Agency.

Why Do We Need CEMS?

CEMS are pivotal in providing evidence that your site is complying with your environmental permit. Failure to comply with your permit can result in fines, forced shut down of operations and a negative impact on your reputation.

In addition to the above, CEMS can provide process data to operators giving confidence that the plant is running as expected. A well-managed CEMS, can provide an early warning that action needs to be taken, before limits are breached.

Do I need CEMS?

The best way to answer your question is for you to refer to your site environmental permit.


Understanding Your Site Permit

Understanding your site permit
Understanding your site permit

In the UK, the monitoring standard for continuous measurement is BS EN 14181. In short:

  • The CEMS you install need to be fit for purpose (QAL1)
  • The CEMS need to be verified and set up correctly (QAL 2)
  • The CEMS need to be checked at regular intervals (QAL 3 – >once per month drift checks & AST – Annual surveillance test)
Schedule 3 Emissions and Monitoring

If your site has the potential to cause damage to the environment, you will need a permit to operate. If your permit stipulates continuous monitoring then you will need to install CEMS.

If the monitoring frequency stipulates periodic (for example, annually or 6-monthly), then you are not required to install CEMS.

Note: while schedule 3 details your emission limits and monitoring requirements, it may be that other areas of your permit will require you to install CEMS. See below example.

Improvement Programme Requirements

My permit stipulates periodic sampling, if I install a CEM, do I still need to complete periodic testing?

Yes. Your permit will detail the minimum monitoring requirements that site have to undertake. If you are required to provide periodic monitoring, then this is what you must do, installing a CEMS will not supersede this.

If my permit does not stipulate continuous monitoring, then do I not need CEMS?

You can operate your plant without reprise from the authorities without installing CEMS. However, the permit stipulates the minimum requirements expected of industry.

Industries today are placing greater importance on reducing their impact on the environment. Better understanding of your emissions will provide this. Indicative monitors can be installed at an affordable price (no requirement for accreditation), providing continuous measurement.

In addition, knowing what you are emitting will provide opportunities for process optimisation.

If you have any questions about CEMS, you can speak to our expert David McGee.

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