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Air Emissions Monitoring

In response to increasingly stringent regulations, plant operators have a growing responsibility to ensure that all air emissions are accurately measured, monitored, and kept within prescribed limits. In this article, we take a look at how air emission guidelines are changing, and how process operators can ensure the accuracy of their air emissions monitoring equipment.

Despite widespread improvements in air quality over recent decades, air pollution globally continues to damage the environment and present a public health risk; causing governments to tighten standards for air emissions.1 As a result, industries are now under more regulatory pressure than ever to minimise air emissions. Analysis of emissions in the UK shows that levels of PM2.5, NOx, SO2, and NMVOCs have decreased drastically over the last three decades. However, the UK government has concluded that further action is required to meet emission reduction targets. As a result, it has committed to “continuous improvement”, meaning opportunities for further emissions reductions will be explored across all sectors.

Many large emitters, including power plants and chemical process operators, shoulder large responsibilities. They must control and continue to drive down their air emissions. This means that reliable and accurate monitoring of emissions is crucial if they are to stay on the right side of ever-tightening legal limits

Installing Continuous Emissions Monitoring Systems (CEMS) enables plants to accurately monitor, track, and report emissions over long periods; although periodic monitoring with portable emissions measuring systems (PEMS) remains popular for some applications, especially where there is relatively low variability in emissions.2

Improving measurement technology in this sector means that high levels of accuracy can be achieved. The best CEMS are capable of measuring over 50 different gas components simultaneously and are often able to detect a few ppm of gas to within 2% accuracy.


The Importance of Emissions Monitoring Equipment Calibration

Regardless of the resolving power of any emissions monitoring system, every measurement it makes is dependent on its initial calibration. It is, therefore, of vital importance that this calibration is performed as accurately as possible for both CEMS and PEMS.

An exact calibration can be achieved through the use of accurate calibration gas mixtures.  Traceability of calibration gases is also important, there should be an unbroken chain of comparisons between any calibration gas with a national or international standard.

Monitoring equipment must be calibrated for each of the gas species to be measured, requiring the use of multiple gas cylinders. This can become problematic when sensors are placed in hard-to-reach places, such as at the top of an industrial stack, as carrying multiple canisters of calibration gases to the sensor to perform calibration can become time-consuming, expensive, and at times be less than ideal from a safety perspective.

Fortunately, the development of multi-component calibration gas mixtures in a single-cylinder has eliminated this problem. By combining multiple gas components at known concentrations within a single gas mix, the number of cylinders required to perform calibration can be drastically reduced, as well as making the actual calibration procedure much faster, and easier to complete.

Air Products produces a range of portable calibration gas products (calibration gas mixtures specifically for the air emissions monitoring market), designed to make calibration in hard-to-reach places as simple and accurate as possible. A single cylinder containing calibration mixtures with up to four different gas components is possible, certified within our ISO 17025 accreditation scope, produced to the highest level of accuracy, ensuring  power plants and process operators can be confident in the calibration of their emissions monitoring equipment and the data and measurements they record.


References and Further Reading

1.           DEFRA Clean Air Strategy 2019. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/770715/clean-air-strategy-2019.pdf. (Accessed: 3rd February 2020)

2.           What’s the Difference Between Continuous Emissions Monitoring and Periodic Measurement? Available at: https://www.auburnsys.com/blog/whats-the-difference-between-continuous-emissions-monitoring-and-periodic-measurement. (Accessed: 18th December 2019)

Air Emissions Monitoring

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