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Environmental monitoring

Fugitive emission technique validation

Supporting development and validation of emissions monitoring technologies

NPL's controlled release testing facility (CRF) can independently validate systems developed to monitor fugitive emissions. This facility provides quantified releases of gas from multiple sources that can be located around sites and within infrastructure to simulate fugitive emissions. Combined with low uncertainty and traceable calibration to primary standards, this system can be used to validate a wide range of systems in their ability to provide accurate measurements of fugitive emissions and locate their sources. Key features include:

  • Highly flexible and reconfigurable allowing bespoke tests to evaluate the performance of fugitive emissions monitoring systems.
  • Fully transportable, modular system for testing products over a variety of emission landscapes by accurately replicating specific source characteristics.
  • Management of complete instrument validation projects, from choosing a suitable test site to validation test protocol design.
  • Versatile system that can validate emissions measurement from both ground-based instruments and aerial observation.

   Flexible system to produce controlled emission of traceable gases mixtures

Our expertise and experience in regulatory compliance, measurement standard development and instrumental optimisation means NPL is ideally placed to advise and guide you through emissions monitoring system and sensor development.

CRF capabilities

The CRF connects an array of gas cylinders to a network of mass flow controllers (MFCs) that provide accurate release of the gases through various distribution nodes. These nodes are connected via hoses and can be located at distances of up to 50 m from the CRF.  


The summary specifications are:

  • Four separately controlled outputs that can release gas at up to 500 l/min per channel.
  • A wide range of gas species can be emitted, such as methane, propane (VOCs), carbon dioxide, nitrous oxide, ammonia.
  • Mass emission rates can be varied from 0 – 55 kg/h for propane, 0 – 20 kg/h for methane, and 0 – 99 kg/h CO2 from each node, with an accuracy of up to 3% of rate.
  • Diluent and interfering gas are controlled via the other two MFCs at flow rates of up to 100 l/min.
  • Computer controlled operation that can log the outputs of all of the MFCs. All can be calibrated and are traceable to the SI using primary piston flow meters.

Typical systems validated

We can validate a wide range of technology used to measure and monitor fugitive emissions. Several systems are described within the BS prEN 17628:2020 standard that sets out the best methods to measure fugitive emissions. Typical systems that could be validated using the CRF include:

  • Differential absorption LiDAR (DIAL)
  • Solar occultation flux (SOF)
  • Mono/bistatic open path systems
  • (Quantitative) Optical Gas Imaging (Q)OGI
  • Hyperspectral imaging
  • (Mobile) tracer correlation,
  • Aircraft and satellite measurements

Further validation via DIAL

In addition to the CRF, NPL can also provide direct measurements of fugitive emissions from sites using the mobile DIAL system. Classed as one of the Best Available Technology (BAT) for fugitive emissions monitoring in the EN 17628 standard and EU refining BREF (BAT reference document), it can provide confirmatory measurement of actual site fugitive emissions for comparison with those installed or operated at the facility. Typically operating for a few days or 1-2 weeks, it can monitor whole site emissions and provide comparison data with defined measurement uncertainty.

Find out more about NPL's Controlled gas release testing facilities 

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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