RESEARCH / DEVELOPMENT / TECHNOLOGY PIPELINE TECHNOLOGY JOURNAL 7 INTRODUCTION Gas detection technologies are essential to safety in meth- ane leak monitoring. Domains of applications are broad, versatile and challenging – gas transmission and distribu- tion pipeline networks, oil and gas production, processing and storage industries, processing industries at large, emergency interventions in confined spaces, etc. in methane gas detection is considerable with the break- through of laser technologies. Combining the strength of laser detection with advances in communication technolo- gies can offer significant added-value and provide tangi- ble benefits throughout the process, from production to end-consumers. Explosion is the primary risk that methane detection technologies protect against. Whenever methane gas is emitted, its interaction with the oxygen present in the atmosphere will increase its flammability. When combined with pressure, this may create an explosion or fire hazard subject to methane gas concentration levels in the air. Methane leak survey applied to gas distribution networks has been used for a long time in efforts to ensure public safety. Since the outset of gas distribution, gas utilities have devised procedures and policies for detecting meth- ane leaks, maintaining, repairing their networks and pre- venting safety hazards. It is no surprise that ensuring the safety of assets, personnel and the public in general is one of the key commitments stated by gas utilities. Over past decades, legislations have also imposed a strict regulatory framework requiring transmission or distribution pipelines to be regularly surveyed following a number of rules. Looking beyond regulatory compliance, economic con- siderations are also a driving force for detecting methane gas. When gas supply has to be shut down in a part of the city to undertake unscheduled repair works on the pipe- line, the financial impact is considerable. In France, for example, after a gas supply disconnection/reconnection, each customer’s installation has to be visually checked by a technician of the French gas distribution company, an extremely long and costly process. But the consequences are nothing to compare with the “worst-case scenario” of a gas explosion occurring in a densely populated area caus- ing material damages and potentially, human casualties. The impact in such cases goes beyond the sole financial aspect, this greatly affects the company’s reputation and image. These “worst-case scenarios” are the nightmares of gas utilities. On a day-to-day basis however, an important factor is the need to reduce ongoing routine maintenance costs and increase operational safety and performance using adequate technologies and detection instruments. In addition to preventing dangerous situations there is the ever-pressing demand of the public opinion and even governments to reduce the carbon footprint of human ac- tivities. Major contributing sources include the gas industry and the methane emissions it generates and explain the need to turn to new technological solutions. The evolution LEAK SURVEY: A MAINTENANCE PROGRAM NECESSITY As part of the leak Detection and Repair programs (LDAR), gas network leak survey is a key contributor to the In- tegrity Management Systems pipeline operators and gas utilities are setting up worldwide. Scheduled leak survey is a powerful tool that enables natural gas operators to know the state of their networks and perform the needed operations, from forecasting and budgeting asset replacement to emergency repair. This takes however a global approach based on a number of key considerations: Analyzing survey procedures to come up with detailed maintenance guidelines is a first key step. This requires taking into consideration the characteristics of the network built over the decades: pipe material (ductile cast-iron, steel, copper, wood, HDPE), date of installation, lay-out techniques, service pressure, the immediate environment (densely urban area or rural area), accessibility of the dif- ferent sections to leak survey teams (on-foot or by vehicle). Past experience feedback as well as risk analysis issues are also taken into account to assign survey priority levels and frequencies to each section of the gas network and determine the human and material resources to be com- mitted. Second, regulatory constraints are setting the global framework. Survey frequency was the first issue addressed, to be followed more recently by the requirement for survey operations’ traceability. The obligation on gas operators to be in the capacity of reporting on any part of a survey oper- ation conducted changes the game completely. It leads to review all the data management process. Then, selecting the best equipment suited to meet all re- quirements is the last step. LEAK DETECTION TECHNOLOGY: THE BREAKTHROUGH OF LASER Leak detection technology has evolved considerably since the early days of gas distribution. If, at the very beginning, leak survey relied on visual inspection of any dead vegeta- tion along pipelines and smell detection – the human nose