Emission monitoring using Differential Absorption Lidar (DIAL)

What is DIAL?

The NPL Differential Absorption Lidar (DIAL) is a sophisticated remote sensing system that provides rapid, accurate measurements of airborne pollutants and greenhouse gases (GHGs) following the protocol described in the European Standard EN 17628:2022. The system is a completely self-contained mobile laboratory that provides 3D mapping of emission concentrations and, when combined with wind information, enables quantification of emission rates for a wide range of target species.

Contact us

Why DIAL?

DIAL is complimentary to techniques such as Optical Gas Imagining and sniffing (as described in European Standard EN 15446:2008) which identify leaks at component spatial level but are not designed to quantify diffuse emissions over wide areas, such as multiple fugitive emission sources (e.g. leaks), vented emissions or emissions from inaccessible areas such as where local atmospheres are potentially explosive. 

DIAL has many advantages over other techniques that are designed to monitor wide areas. DIAL is substantially more flexible than Solar Occultation Flux (SOF), in that it has no need for specific daytime weather conditions or solar position, and it is not dependent on sunlight. DIAL also provides ranged resolved information that allows emissions to be located accurately, and DIAL is much less dependent on making assumptions about the dispersion of emissions compared to techniques such as Reverse Dispersion Modelling (RDM) and Tracer Correlation. 

These strengths have been recognised in various publications, include the “Best Available Techniques (BAT) Reference Document for the Refining of Mineral Oil and Gas” (Industrial Emissions Directive 2010/75/EU) where it is referenced as a key method to determine industrial emissions. For more information on the technical specifications of DIAL, please see the document available at the link below. 

Learn more about DIAL (PDF)

Where has it been used?

The DIAL technique has been used for a number of atmospheric monitoring campaigns, including:  

• remote measurements into inaccessible, hazardous or elevated areas  
• wide area surveys of diffuse sources, including methane from landfill sites  
• measurement of total industrial site emissions, including flares and tanks 
• boundary fence monitoring 
• identification and quantification of leaks and fugitive emissions  
• plume tracking and source identification from complex industrial plant  
• environmental impact assessment. 

Advantages of DIAL 

• Mobile: Can be rapidly deployed to measure at a wide range of sites including petrochemical, landfill and agricultural.
• Self-contained: There is no requirement for additional support infrastructure to operate, all equipment and power are contained in a single trailer.
• Identify specific pollutants: Can operate in heavily polluted environments since it is highly selective of the gas of interest and not significantly affected by other gases.
• Track record: The NPL design has a 30-year proven track record of reporting emissions for commercial and governmental customers.
• Flexibility: There is no requirement for clear skies or good visibility, monitoring can be carried out under a wide range of conditions including night time.
• Monitoring in ‘real time’: the on board scanner allows the system to survey over a complete hemisphere from one location so that multiple sources can be surveyed in real time.
• Spatial Detail: The system provides spatial information allowing the source of emissions to be clearly identified, tracked and separated from other potential sources.
• Traceability: The accuracy and uncertainty of the NPL DIAL can be traced to national gas standards, which provides total confidence in the monitoring. 

Accessing NPL’s emission monitoring service

If you would like more information about how to access NPL’s DIAL emission monitoring service, please contact us using the link below.

Obtaining a DIAL system 

As well as providing DIAL measurement services, NPL has built and provided DIAL systems to support emission monitoring by other organisations. For further information on how NPL can supply a DIAL system for your organisation please contact us using the link below.

Contact us