Innovate UK Real Time Detection of Respirable Crystalline Silica (RCS)

Lead Research Organisation: University of Hertfordshire
Department Name: School of Physics, Astronomy and Maths


The concept behind this project is based on the use of spatial light scattering (SLS) analysis and related optical technologies to enable differentiation of Respirable Crystalline Silica from other ambient dust particles. It will consist of a miniature optical particle sampling chamber that will enable RCS particles to be individually identified, counted and sized separately from the background dust. When coupled with suitable data processing electronics and software to include particle loss mechanisms, density and other factors, the completed detector unit will provide a real-time output of RCS mass concentration in the environment. Being crystalline in nature, fracking sand splinters into particles that have facetted surfaces, i.e. flat mirror-like fractures, and it is this particular characteristic of RCS dust that forms the basis of the project. When passed through an illuminating light beam (such as that from a laser), faceted particles result in scattering patterns which are highly asymmetric about the beam axis, unlike virtually all other particle morphologies. This means that the Centroid of Intensity (COI), or the 'centre of gravity' of the light pattern of an RCS particle lies a significant distance from the axis, in contrast to those of other particles which are close to it. So, by setting a discrimination radius around the axis only facetted particles will be registered. RCS particles may represent a small percentage of the total particle population so a viable sensor would need a high throughput (typically ~ 10,000/second) so calculating the COI using conventional image processing techniques is impractical. Position Sensitive Devices (PSD), offer an ideal solution being low cost and producing accurate X-Y analogue outputs defining the COI of the light falling on the chip. Thus, a simple empirically-determined 'threshold' distance of the COI from the pattern centre allows differentiation of facetted particles patterns. An additional 'orthogonal' optical measurement, such as birefringence or fluorescence, will also be incorporated to provide a high discrimination level and minimize false-positive RCS detection. The project will involve close collaboration between Trolex and the Particle Instruments Research Group at the University of Hertfordshire. The University will be responsible for the sensor technology development, the design of the detection chamber and optics, and laboratory evaluation using prepared dusts. Trolex will be responsible for producing a fieldable technology demonstrator instrument that will enable the detector output to be presented as a real-time RCS density in a real-world environment.

Planned Impact

The use of Silica in fracking represents a risk to both workers and the environment that has not yet received much publicity in the UK. There are considerable benefits in understanding and managing the risks associated with RCS exposure. Risks surround health and safety of workers and local inhabitants. Most national regulators have a detailed awareness of the medical basis of risks and have developed permissible exposure limits (PELs) and recommended exposure limits (RELs). Proposed OSHA PEL's for RCS are estimated to protect 2.2m workers (mostly in construction, 1.85m) with the remainder in general industry including foundries and fracking. New PEL is 50ug/cum air over 8 hour day. Net benefits are estimated at between US$2.8 - 4.7 bn/yr with up to 800 lives saved/yr in the US alone across all at-risk industries. Currently the UK limit for Respirable Dust is 4mg/m3 and for RCS 0.1 mg/m3. UK legislation is currently written around personal sampling for worker exposure however area sampling in real time will still help worker safety. Fixed perimeter monitoring would warn operators if dust or RCS levels approached concern levels for pollution of neighbouring areas. Permanent records will allow reliable, low cost, compliance monitoring. Monitoring RCS in real time ensures that workers are properly protected and that current operations are compliant with existing regulations. Formulation of new regulations is also assisted. The introduction of this new technology will advance the UK's position as a technical centre of innovation and excellence in the world industry. Adoption of this technology will accelerate the growth of the company and its distributors, developing the requirement for skilled labour both in manufacture and support which will be based in the UK, producing additional tax revenue. More than 98% of the shale gas activity and potential market will be outside the UK so considerable export revenues will accrue to UK plc. The availability of this technology could speed the development of the shale gas industry. In the UK a recent IoD report estimated 74,000 jobs could be supported by the industry and its supply chain. Spending by the employees would benefit local businesses. Environmental benefits are concerned primarily with minimising risks of RCS exposure. The replacement of costly time-lapse RCS monitoring will improve the health and safety of workers on site and reduce overall cost of operation as well as allowing earlier intervention in case of operational problems.


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Hesse E (2015) Modelling light scattering by absorbing smooth and slightly rough facetted particles in Journal of Quantitative Spectroscopy and Radiative Transfer

Description KEEP+ European Regional Development Fund
Amount € 50,000 (EUR)
Organisation European Union 
Sector Public
Country European Union (EU)
Start 02/2018 
End 10/2018
Description Trolex Funding
Amount £22,000 (GBP)
Organisation Trolex Ltd 
Sector Private
Country United Kingdom
Start 04/2015 
End 10/2015
Description Trolex Ltd Respirable Crystalline Silica Detection and Monitoring. 
Organisation Trolex Ltd
Country United Kingdom 
Sector Private 
PI Contribution Our research team have developed several possible techniques for the detection of airborne crystalline silica particles and have tested these in the laboratory.
Collaborator Contribution Trolex have produced 'hardened' prototype of some of our laboratory instruments and have field tested these in industrial locations, many representing extreme environments, such as mines and tunnel constructions. In 2018 Trolex bagan the manufacture of prototype airborne RCS monitors with a view to these being tested in 2019 and a commercial RCS Detector product produced by late 2019.
Impact Patent. Contact with other commercial end-users of possible detection instruments.
Start Year 2013
Title Detecting respirable crystalline particles 
Description This patent application arose from the collaborative research undertaken with Trolex Ltd funded by the award : Innovate UK Real-time Detection of Respirable Crystalline Silica (NE/N004744/1). Respirable Crystalline Silica (RCS) is one of the major health and safety issues surrounding the fracking process. Whilst attention in the UK has focused elsewhere, considerable experience has been obtained in the US about the safety implications involved in fracking. Crystalline silica sand is one of the most important components of the process and whilst not hazardous itself its use creates a very dangerous respirable dust containing shard-like silica particles. This dust is well established as a serious health hazard, causing silicosis and a variety of other life threatening conditions. Current methods of monitoring the amount of RCS in the atmosphere rely on its collection through a filter over a period of time followed by laboratory analysis taking up to 2 weeks, by which time any damage has already been done. The objective of this project was to establish the feasibility of developing a sensor that is capable of measuring the concentration of RCS in the atmosphere on a continuous, real-time, basis. Such a sensor was to be based on a novel approach to identifying the particular physical characteristics of Crystalline Silica particles using a combination of innovative optical processes. The principal achievements of the feasibility study were: • A prototype Sensor Module was developed that records in real time both birefringence and optical scattering parameters from individual airborne particles at high throughput rates. As far as we are aware, this capability is unique in the world of airborne particle monitoring. • The initial statistical analyses of data recorded by the Sensor Modules suggest that a detection technique for fracking sand aerosol may well be feasible. There were therefore strong grounds for pursuing the technique further, and acquiring additional funding for this is underway. 
IP Reference GB1509926.0 
Protection Patent application published
Year Protection Granted 2016
Licensed Yes
Impact It is too early to assess impact of the developed technology, but if successfully developed into a product by Trolex it will have widespread application is occupational aerosol monitoring as well as the intended application of monitoring RCS releases from shale gas extraction sites..