DIAL is a sophisticated remote sensing system which is a completely self-contained mobile laboratory
The Differential Absorption Lidar (DIAL) system remotely monitors atmospheric pollutants at ranges of up to 500 m. DIAL measurements are real-time, directly traceable to primary standards of gas concentration and are free from interference and contamination.
The DIAL system carries a suite of additional measurement equipment to monitor meteorological parameters and ambient gas concentrations.
Species the DIAL system can quantify:
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The NPL design has a 30-year proven track record of reporting emissions for commercial and governmental customers.
The DIAL technique
The DIAL technique uses a laser source of tuneable wavelength that is transmitted over the measurement region. A small fraction of this light is scattered back by the aerosols and particulates that are present in the atmosphere; this is collected with a telescope and a fast, sensitive detector. The extent of the absorption is known from accurate laboratory data, enabling the concentration, and spatial distribution, of the atmospheric pollutants to be determined. This data is combined with wind information to provide a direct measurement of the mass emission rate of the target species.
Obtain a DIAL system
Access NPL’s DIAL measurement services
As well as providing DIAL measurement services, NPL has built and provided DIAL systems to support emission monitoring by other organisations.
For more information, contact us today using the link below.
Why DIAL?
Capabilities and benefits
- DIAL is an active technique which can operate in a wide variety of environmental conditions. There is no requirement for the sun or clear skies with measurements possible at night.
- Range resolved concentration measurements remove the need for assumptions about plume dispersion in the atmosphere. Assumptions on the application of the appropriate wind are also reduced.
- Sub-site (functional element) scale measurements give granular information on areas or assets with highest emissions, allowing for mitigation efforts to be targeted where they could have the greatest impact.
Industrial Emissions Directive 2010/75/EU
This includes 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.
European standard
The European Committee for Standardisation (CEN) has published the standard method EN 17628:2022 for the measurement of fugitive emissions of VOCs. This document has been prepared by the Technical Committee CEN/TC 264/WG38, led by NPL, and it includes the use of DIAL, which is based on the NPL DIAL method. The standard sets out the performance requirements and capabilities of the direct monitoring methods, the requirements for the results and their measurement uncertainties. It is applicable to all the species measured with DIAL in addition to VOCs.
DIAL is complimentary to techniques such as optical gas imaging and sniffing
The European Standard EN 15446:2008 supports identification of leaks at component level using sniffers and OGI, but it is not designed to quantify diffuse emissions over wide areas that are covered by EN 17628.
The DIAL technique can be used for a number of atmospheric monitoring campaigns, including:
Remote measurements
Into inaccessible, hazardous or elevated areas.
Wide area surveys
Diffuse sources, including methane from landfill sites.
Total site emissions
Measurement of total industrial site emissions, including flares and tanks.
Boundary fence monitoring
Perimeter measurements to track emissions at site boundaries.
Leak detection
Identification and quantification of leaks and fugitive emissions.
Plume tracking
Source identification from complex industrial plant.
Environmental impact assessment
Assessment of environmental impact based on measured emissions.
Data analysis and interpretation
DIAL's unique software enables total site emissions to be visualised via a series of multi-dimensional concentration plots, in a way that highlights key emission points and their concentrations.
A team of experts at NPL
Our team at NPL can give advice on data analysis and interpretation. We have an in-depth technical knowledge of the operations of industrial plants, an awareness of potential emissions and extensive experience in solving complex atmospheric measurement problems.
Atmospheric pollutants
Here at NPL, our use of DIAL enables us to collect real-time data for gaseous species with characteristic absorptions from the ultraviolet through to the mid-infrared spectral region. Our ability to detect a wide range of atmospheric pollutants emitted by oil refineries is what sets our capabilities apart from other techniques used in the refinery arena.
By utilising this advanced technique, we can quantify species including methane, ethane, general hydrocarbons, CO2, HCl, benzene, toluene and SO2.
Our plans for future development include measuring NO and NO2 to further expand on our service offering.
Validation
Field validation exercises against known reference emissions have confirmed that the NPL DIAL system yields measurements of mass emission rates which are linear with release rate, fall within the stated variability for the measurements, and the systematic biases in the DIAL measured emission rate are less than 4%.
Explore more NPL instruments
NPL has a wide range of standard instruments for taking accurate measurements. We work collaboratively to design and manufacture innovative measurement instruments.
Interested in our emissions services?
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