Researchers at the Anhui Institute of Optics and Fine Mechanics at the Chinese Academy of Sciences have developed a method to create a 3D image of a leaked gas cloud. The image provides detailed information about the leak, such as its location, volume, and concentration. The automated detection approach could be used to provide early warnings, assess risk, and help determine the strategies to fix the leak, the researchers said. “With the rapid development of society, there are now large facilities located around the world where toxic, harmful, flammable, and explosive chemicals are being stored,” said research team leader Liang Xu from the Anhui Institute of Optics and Fine Mechanics. “If there is a leak at one of these facilities, it’s important to quickly understand its composition, concentration, location, and distribution.” Researchers developed a way to reconstruct 3D images of a leaked gas cloud and overlay the information on a digital map. The method provides detailed information about the leak such as location, volume, and concentration. Courtesy of Yunyou Hu/Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. The method combines information from two remote Fourier-transform infrared spectroscopy (FTIR) imaging systems with precise positioning information from gyroscope sensors and GPS to create a 3D image of the gas cloud superimposed on a Google Earth digital map. “Previously, when leaks occurred, the specific location and direction the gas was moving could not be determined,” said Yunyou Hu, first author of the paper introducing the approach. Hu said that the method can be used to accurately find the latitude and longitude of the leaked gas — information that helps to determine who might be exposed, and for quickly stopping the leak. FTIR spectroscopy is favored in the remote quantitative detection of gaseous pollutants due to its high sensitivity, high resolution, and ability to perform real-time measurements with a detection range of about 5 km. However, a single FTIR remote-sensing imaging system only provides 2D information about a gas leak. A 3D gas-sensing method combines information from two remote Fourier-transform infrared spectroscopy (FTIR) imaging systems. The systems deliver precise positioning information from gyroscope sensors and GPS. Courtesy of Liang Xu/Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences. To obtain a 3D picture, the researchers used two systems to make 2D measurements of a gas cloud from different perspectives. This information was then spatially registered with location information obtained using the gyroscope sensors and GPS. Putting the data into a computerized tomography imaging algorithm called simultaneous algebraic reconstruction technique (SART) produced a 3D reconstruction of the gas cloud. Each 3D pixel in the 3D reconstructed gas cloud contains 3D information. The team tested its method in an outdoor field experiment. The team used two scanning FTIR remote sensing imaging systems to perform remote monitoring of small amounts of sulfur hexafluoride and methane released over two minutes in a space of about 315 m3. Team members generated 3D re-creations of the gas clouds with longitude, latitude, altitude, and concentration distribution for both gases. “To apply our technique in a real-world scenario, two or more scanning FTIR imaging systems would need to be installed around the monitored area to form a cross-scanning network,” Hu said. “Our proposed method could then be used to create a 3D reconstruction of a leaking gas cloud that could, in turn, be used to find the leak source and provide early warning information.” The team is working to optimize the reconstruction method and plans to test the system in real industrial environments. The research was published in Optics Express (www.doi.org/10.1364/OE.460640).