Vehicle prototype detects methane on the move

As the SUV drove through urban roads and highways, its onboard spectroscopic system took a methane reading once per second. Researchers at East China Normal University completed a 1-hour, 47 km road test, with the vehicle reaching a top speed of 100 km/h. They used a controlled-release device to simulate a natural gas leak and track the location of the gas plume.

The equipment can measure methane with a precision of 66 ppb. It packs mid-infrared dual-comb spectroscopy into compact hardware: two precisely matched frequency combs provide multiple evenly spaced wavelengths, while mid-infrared light passes through an open-path gas cell to create a 25 m optical path through the surrounding air. Many molecules have distinctive absorption signatures in the mid-infrared region, making it suitable for sensitive gas identification.

The challenge of mobile measurement is not simply mounting the instrument on a vehicle. Environmental noise and vehicle vibrations can affect the performance of dual-comb spectroscopy systems, and the research team refined the design to address this problem. During testing, the system measured an average background methane concentration of 1.815 ppm, with stable results. A two-dimensional concentration map generated after the vehicle drove around a simulated leak site also closely matched local wind patterns. The findings were published in Optics Letters, and the system achieved a figure of merit of 3.4 × 10⁶ Hz, comparable to that of typical laboratory mid-infrared dual-comb spectroscopy systems.

In practical terms, this means cities and natural gas companies could use a vehicle to search for leak hotspots invisible to the naked eye without first deploying hardware on site. The system can also record GPS coordinates and notify maintenance crews, helping direct repair efforts more accurately. Natural gas infrastructure, landfills, livestock farms and coal mines could all become targets for mobile inspections. Methane leaks may also create fire and explosion hazards, so more accurate detection could both reduce resource waste and potentially improve air quality for nearby residents.

But it is not yet a ready-to-use commercial inspection product. The research team plans to expand the spectral coverage to detect multiple trace gases simultaneously, suppress baseline drift during long integrations and develop automated analysis software suited to large volumes of mobile data. The team also hopes to further reduce the equipment’s size, weight and cost, ultimately integrating it into a drone for use in areas that are difficult to reach by road.