The need
Fourth State is a small to medium sized enterprise (SME) that manufactures ozone and nitrogen oxide (NOx) gas generators, based on patented air plasma technology. Their mission is to make the biochemical benefits of reactive oxygen and nitrogen species (RONS) accessible, using just air and electricity as inputs to modular and user-friendly plasma reactors. RONS have well-established antimicrobial, bioactive and chemical effects, and could be used for decontamination, therapeutic and bio-/chemical process engineering applications, enabled by Fourth State’s products and services.
During the pandemic, Fourth State received a large order from a customer looking to use their air plasma technology to implement automated disinfection in public spaces. This required a rapid response from Fourth State to scale up manufacturing and quality assurance for its ModuNOx™ modular generators. In order to deploy the technology safely and effectively at scale, the company needed help measuring RONS in the air plasma output. The pandemic also ignited an increased interest in using Fourth State’s NOxLab™ R&D products, which allow laboratories to explore and rapidly develop additional antimicrobial, bioactive and chemical applications of RONS.
At the time, no off-the-shelf measurement solutions were available which could measure all RONS of interest, to high precision, over the relevant concentration ranges, and without cross-sensitivity. Fourth State had previously worked with university partners for initial chemical characterisation of its prototypes, but required NPL’s gas metrology expertise to deliver robust product testing.
The solution
NPL has extensive experience in the development and dissemination of nitrogen monoxide (NO) and nitrogen dioxide (NO2) primary reference materials in high pressure compressed gas cylinders, as well as in the accurate and traceable measurement of nitrogen oxides (NOx = NO + NO2) and reactive nitrogen compounds (NOy). NPL also maintains the UK national ozone (O3) standard. NPL is home to many real-time, high precision gas analysers and industry leading expertise in their operation and accurate calibration.
To help Fourth State quantify O3, NO, NO2, NOy, NOz (the sum of all higher oxides of reactive nitrogen oxides, NOz = NOy – NOx) in the output of the RONS generator, under different flow regimes, NPL developed a bespoke experimental setup that facilitated simultaneous measurements by multiple instruments. Due to the flow rate requirements of the gas analysers used, it was necessary to dilute the output of the RONS generator to provide sufficient flow for all instruments to sample simultaneously. This required accurate and precise flow control to enable accurate quantitation for all compounds in the RONS output.
NPL also conducted a review of relevant and potentially applicable regulations and standards and created product testing specifications and criteria for Fourth State to employ.
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A NOxLab™ RONS generator, showing air inlet, flow controller, power input and user controls
The impact
NPL accelerated Fourth State’s time to market, allowing them to rapidly deliver verified air plasma generator modules at high volumes (ModuNOx™ OEM Solutions) to their customer, enabling the provision of automated disinfection in public spaces. The work also enabled the delivery of calibrated laboratory equipment (NOxLab™ R&D Products) to multiple leading international research institutes, allowing them to explore and rapidly develop novel antimicrobial, bioactive and chemical applications. NPL carried out this work as part of the Measurement for Recovery (M4R) programme.
Fourth State benefitted from new technical knowledge, skills, improved process methods and test setups which will be used in future product testing and R&D. Fourth State also secured a £50k grant for further development of the RONS measurement setup at NPL, through Innovate UK’s Analysis for Innovators (A4I) programme.
The Fourth State team during their visit to NPL alongside members of the Gas Metrology group. From left to right; Phillip Thomas, joint PhD student from the University of Surrey and Fourth State; Calum Bavin, Gas Metrology Scientist; Gavin Sandison, Fourth State VP of Engineering; Thomas Harle, Fourth State CEO and Founder; Tom Wantock, Fourth State Research and Innovation Manager; Dave Worton, Gas Metrology Principal Scientist; and Sivan Van Aswegen, Gas Metrology Higher Scientist. Other members of the project team not in the photo are: Nick Martin , Air Quality and Aerosol Metrology Principal Scientist, Bryan Sweeney, Air Quality and Aerosol Metrology Senior Scientist and Rod Robinson, Emissions and Atmospheric Metrology Principal Scientist.