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In hazardous areas, where there are leaks of hazardous chemicals, array monitoring and tracking of the source of such leaks are necessary. In refineries and chemical processing plants, there are many high-risk areas with vulnerable sealing points that are prone to leakage, as well as areas susceptible to corrosion. Such locations are usually inspected only once a week or once a month. In old and large-scale hazardous source installations or tank farms, the absence of a GDS system for detecting toxic, harmful, flammable, and explosive gases creates blind spots in leak detection ； If detectors for toxic, harmful, or flammable and explosive gas leaks are added, wiring work becomes more difficult and costly. For newly built or relatively new refining and chemical plants, if only a small number of detectors for toxic, harmful, flammable, or explosive gases are installed, it is difficult to manually locate the source of the leak after audible and visual alarms are triggered in the control room or on the ground – errors in alarm detection or leaks from other equipment carried by the wind can complicate things. The process takes a long time (usually 1–4 weeks), and it is costly as it requires significant manpower and resources, in addition to posing operational risks. After an alarm is triggered in the GDS system of high-risk petrochemical plants, if the source of the leak cannot be located promptly, the supervisors in charge of the plant and its operations will suffer greatly. In the event that an unplanned shutdown of the plant or an accident related to safe production occurs due to a flash explosion, poisoning, or fall while using manual portable instruments to locate the leak, the consequences could be disastrous. A monitoring and leak localization system for hazardous chemical leaks in high-risk petrochemical facilities’ dangerous areas employs wireless gas concentration detectors and anemometers to measure wind speed and direction, based on gas leakage diffusion models. It utilizes source strength inversion models and positioning algorithms to quickly locate the source of leaks, enabling timely warnings of potential leakage risks and rapid identification of the location where leaks occur. This system offers high precision in leak localization and accurate risk assessment, improves the efficiency of leak detection in such facilities, helps to prevent or reduce safety incidents resulting from leaks, enhances the process safety level of petrochemical plants, and ensures their stable operation. The array monitoring and leak localization system for hazardous chemical leaks in hazardous areas is suitable for high-risk petrochemical facilities such as ethylene cracking, xylene adsorption separation, syngas/coal gas production, ammonia cooling, ammonia synthesis, natural gas purification, S-ZORB desulfurization, and gas holders, as well as ammonia-cooled warehouses or machine rooms in the cold chain industry ； It has been applied to platforms at high elevations in ethylene cracking and xylene adsorption separation units, where there are numerous high-risk leakage points. Typical success case of the array monitoring and leak tracing system for hazardous chemical leaks: In an olefin processing plant, there are numerous heat exchanger valves and flange seals on a platform 60 meters high; the working medium is a mixture primarily composed of olefins. The equipment pipelines are exposed to alternating high and low temperatures, resulting in a high risk of leaks. Based on the leakage risk map, a “backward-Z” array of radiochemical detectors was installed on-site (the ☆ in the diagram represents wireless gas concentration detectors). In the first week after the system was put into operation, the average medium concentration (MG/L) measured by each detector during that first week, along with wind direction diagrams, were marked on the detector layout map. This allowed for an initial assessment that there were sources of emission upwind of detectors SN11120002 and SN11120007, while there was a leak at the flange connection upwind of detector SN11120009, with a relatively small amount of leakage. The leak localization software is based on the Gaussian plume-patch intermittent diffusion model; it integrates the monitoring data from the same wind direction, and utilizes a patented model and algorithm for reverse calculation of source strength to quickly locate the source and intelligently determine the leakage risk level at that location. Detectors SN11120002 and SN11120007 continuously detected the leaking medium, indicating the presence of a significant leakage source 5-10 meters outside the boundary of the hazardous area under investigation or monitoring in this case. The hazardous area array monitoring and leak tracing system, under the condition that the deployment density is not higher than that of the GDS system for detecting and alerting toxic and harmful gases, is capable of determining the source intensity of the leakage at a distance of 5–10 meters upwind from the detector locations, better than the GDS system. It enables early warning of the risk level associated with leakage sources, thereby reducing the safety risks for personnel carrying out inspections. This system also improves the efficiency of identifying leaks in refining units or ammonia cooling rooms, and helps to prevent or reduce unplanned shutdowns or safety incidents caused by the leakage of hazardous gases. Investment returns of the array monitoring and leak tracing system for hazardous chemical leaks: A hydrocracking unit has been in operation for many years, and the air coolers located at the top of its distillation tower are prone to corrosion and leakage; the leaked gases or volatile organic compounds typically escape into the ambient air through plug seals. If minor or localized corrosion leaks in the air cooler are not detected in a timely manner, such minor leaks can rapidly develop into severe leaks, resulting in an unplanned shutdown of the equipment ； If the leaking medium contains high or concentrated levels of hydrogen sulfide or ammonia, it can also cause poisoning in personnel carrying out spot inspections, leading to injuries or even fatalities. To avoid unplanned shutdowns and poisoning incidents among inspectors, 500,000 yuan was invested to install an Internet of Things system for array-based monitoring and leak tracing; specifically, 4–5 wireless detectors for light hydrocarbon VOCs and hydrogen sulfide gas were deployed on each side of the air cooler’s inlet and outlet pipes (the red areas in the diagram indicate the corroded and leaking pipe bundles). This air cooler has two inlets and two outlets, with a total of 40 wireless detectors for monitoring leak gas concentration installed. If traditional wired detectors for toxic and harmful gases are used, and an equal number or density of detectors is installed, the cost of cable installation will exceed 500,000 yuan ； If a gas cloud telemetry instrument is used, the cost of purchasing such an instrument exceeds 800,000 yuan ； If online monitoring is carried out using an infrared thermography camera, only severe corrosion leaks can be detected, making it difficult to avoid unplanned shutdowns of the equipment due to such corrosion leaks. The lifespan of wireless gas concentration detectors is over 4-5 years (including battery replacement costs). Assuming that this air cooler requires shutdown for repairs once a year, the cost of fixing minor leaks is 100,000 yuan, the cost of fixing significant leaks is 300,000 yuan, and the cost of fixing severe leaks that cause unplanned shutdowns of the unit is generally over 500,000 to 1,000,000 yuan ； Therefore, the investment return for this project will be between (30 - 10) * 4 - 50 = 300,000 yuan and (50 - 10) * 4 - 50 = 1,100,000 yuan.