Researchers at East China Normal University have developed a vehicle-mounted spectroscopy platform capable of detecting and geolocating methane emissions while driving. The system is designed to combine laboratory-level measurement precision with mobile operation and could support future monitoring of gas networks, industrial sites and other critical infrastructure. Methane emissions are not only a major climate concern but can also represent a direct safety risk. Leaks from natural gas infrastructure may create fire and explosion hazards, while remaining difficult to identify because methane is invisible and can disperse rapidly depending on wind and local conditions. A research team at East China Normal University has now demonstrated a mobile detection system designed to identify such emissions in real time from a moving vehicle. The technology, described in the journal Optics Express, is based on mid-infrared dual-comb spectroscopy and can combine gas concentration measurements with geographical positioning data. According to the researchers, this could allow vehicles equipped with the system to patrol residential areas, industrial zones or pipeline corridors and identify abnormal methane concentrations without requiring measurement equipment to be installed at the site in advance.
Dual-comb spectroscopy moves beyond the laboratory
At the core of the platform is mid-infrared dual-comb spectroscopy. The method uses two precisely coordinated frequency combs – light sources generating a large number of evenly spaced optical frequencies. The mid-infrared range is particularly suitable for gas analysis because many molecules exhibit strong and characteristic absorption signatures within this part of the spectrum. This allows different gases to be detected and measured with high sensitivity. Dual-comb spectroscopy has already demonstrated high accuracy in laboratory environments. Mobile deployment, however, introduces considerably more challenging conditions. Conventional systems depend on precisely aligned optical components and are sensitive to vibration, temperature changes and other environmental disturbances. These limitations become especially important when the objective is to search for previously unknown emission sources. Methane plumes may be distributed over large areas and can continuously shift as wind conditions change. To make the technology suitable for use on the road, the researchers developed vibration-resistant fibre lasers and a method that enables the two frequency comb sources to remain synchronised without complex active phase-control hardware. The mid-infrared light is fed into a compact open-path gas cell providing an effective optical path length of 25 metres through air drawn from the surrounding environment. The extended interaction distance increases measurement sensitivity without requiring a correspondingly large instrument.
Measurements at speeds of up to 100 km/h
A key advantage of the new platform is its ability to conduct measurements while the vehicle is moving. According to the research team, the system can operate at vehicle speeds of up to 100 km/h while maintaining measurement performance close to that achieved by laboratory-based dual-comb spectroscopy systems. Gas concentration data can also be linked to GPS coordinates, allowing areas with elevated methane levels to be geographically identified. The concept therefore opens the possibility of systematically surveying gas infrastructure from the road. If an underground pipeline were leaking, for example, a monitoring vehicle could detect an increase in methane concentration, record the position and provide maintenance personnel with information on the likely location of the emission. The researchers also emphasise that the hardware is compact, relatively energy-efficient and based on a modular plug-and-play architecture – characteristics that could facilitate integration into other mobile platforms.
47-kilometre road test validates mobile performance
The system was initially tested during short drives on a university campus at speeds of approximately 20 km/h, with measurements taken at several locations. This was followed by a one-hour road test covering 47 kilometres across urban roads and expressways. Vehicle speeds reached up to 100 km/h, with measurements recorded every second. During testing, the system achieved a figure of merit of 3.4 × 10⁶ Hz, a level comparable with typical laboratory-based mid-infrared dual-comb spectroscopy systems. Methane was measured with a precision of 66 parts per billion, while water vapour measurements reached a precision of 114 parts per million. During the long-distance road measurements, average background methane concentrations were recorded at 1.815 ppm, while average water vapour levels were 1.072%. The stability of these baseline measurements is particularly relevant for mobile leak detection because local increases can then be distinguished from normal atmospheric concentrations.
Controlled methane releases successfully located
The researchers also conducted controlled methane-release experiments to assess whether the system could detect individual emission sources rather than merely measure background concentrations. The vehicle drove past two simulated natural gas leaks and successfully detected and geographically located both methane plumes. In another test, the researchers drove repeatedly around one emission source and used the measurements to generate a two-dimensional methane concentration map. The resulting distribution corresponded closely with the prevailing local wind conditions. The experiments demonstrated that the platform could distinguish between normal atmospheric methane concentrations and significantly elevated gas-plume signals while operating under real outdoor conditions. They also confirmed that the optical hardware could withstand vehicle vibration and changing road environments without compromising the system’s ability to identify methane emissions.
Potential applications extend beyond gas networks
Natural gas infrastructure represents one of the most obvious potential applications, but the technology could eventually support monitoring across a much wider range of environments. Methane is emitted from sources including livestock facilities, landfills, coal mines, oil and gas production sites and other industrial installations. Many of these emission sources cover large areas, making continuous monitoring difficult with conventional stationary sensors alone. Vehicle-mounted detection could therefore provide an additional mobile monitoring layer capable of surveying extensive areas and identifying local concentration hotspots. For operators of gas infrastructure in particular, improved localisation could have both environmental and operational advantages. Detecting leaks more accurately could support targeted maintenance interventions, reduce the loss of natural gas and shorten the time required to identify potentially safety-critical faults. At the same time, more detailed measurement data could help cities and industrial organisations quantify methane emissions that would otherwise remain difficult to detect and support the development or verification of emission-reduction measures.
Drone integration planned
The research team is already working on further development of the platform. One objective is to extend its spectral coverage so that several trace gases can be measured simultaneously. The researchers also plan to further reduce baseline drift during long measurement periods and develop automated software capable of analysing the large volumes of data produced during mobile surveys. Additional miniaturisation is intended to reduce the system’s size, weight and cost. Ultimately, the researchers want to integrate the spectroscopy platform into unmanned aerial vehicles. Drone-based deployment could extend methane monitoring beyond accessible road networks and enable surveys of pipeline routes, industrial sites and other difficult-to-reach areas. The development illustrates a broader shift in gas monitoring from isolated measurement points towards mobile, georeferenced detection. For operators of critical gas infrastructure, such systems could ultimately combine environmental monitoring with an operational safety function: identifying abnormal gas concentrations across large areas and providing maintenance teams with more precise information on where potential leaks are located.
