## 5 Discussions and Recommendations
* _Control measure planning_: Areas with high VOC concentrations may be subject to stricter monitoring and specific interventions, such as using protective barriers, increasing local ventilation, or installing equipment to capture the vapors. * _Data-driven decision making_ in situ: The refineries can integrate cluster analysis into their monitoring and reporting systems. This integration can support operational and strategic decisions, providing a clear perspective on critical areas and periods concerning emissions. The main directions through which our results can support the strategies to be applied in the maintenance scheduling of the tank of the equipment in the reservoir parks and the compliance with the environmental regulations are:  
* _Optimizing the equipment monitoring programs_. The statistical characteristics of the series and the series clustering indicate areas with high levels of emissions or pronounced variability in VOC concentrations. This information can be used by companies to prioritize verification activities in critical areas, thus reducing the impact of emissions on the environment. For example, for areas 1 and 2, where maximum values and standard deviation were high, operations carried out to establish the operational safety level of the industrial equipment (which are periodically performed to verify the integrity and/or tightness of valves, pipes, and, implicitly, tanks, as well as hazard warning systems) must be prioritized, under stricter safety measures, or scheduled during periods with favourable meteorological conditions. * _Taking measures for reducing emissions as much as possible_. By classifying the distribution of VOC emissions, the areas that require additional mitigation strategies are highlighted. For example, points/places with maximum concentrations or high variability can benefit from improved sealing methods by applying best available techniques (BAT) based on the requirements of Directive 2010/75/EU implemented by European Commission decision 2014/738/EU and the use of vapor recovery systems or more stringent operational controls during verification periods [48]. * _Removing non-conformities based on environmental regulations_. Digital representations of pollutant distribution (spatial distribution maps) and clustering provide a solid framework for observing compliance with air quality standards. By quantifying accepted emission levels in the industrial environment (the accepted average hourly concentration for the volatile non-methane organic compounds is between 0.15 and 10 g/Nm\({}^{3}\) during the operation period) and identifying critical areas, refineries can develop reporting mechanisms and develop action plans to comply with the legal requirements. * _Continuous monitoring_. The methodologies used in this study (statistical feature analysis and clustering) can serve in developing real-time monitoring systems that can be deployed during the revision periods to provide early warnings and support response actions to increases in emissions, thereby improving operational safety and decreasing environmental pollution. International studies on refineries indicate a wide range of VOC concentrations, influenced by factors such as the type of stored products, control measures implemented, and local climatic conditions. For example, the VOC emission inventory by [PERSON] et al. [49] at the Shandong refinery in China (with an annual crude oil processing capacity of 12 million tons) found that petroleum product storage areas were the largest sources of VOC emissions, accounting for 56.4% of the total emissions at the refinery, followed by petroleum loading/unloading operations, the wastewater collection and treatment system, the ventilation outlets of the installations, and leaks from industrial equipment. Another study conducted by [PERSON] et al. [50] assessed the environmental impact of the chemical/petrochemical complex, which includes the crude oil refining sector in Tarragona from 2015 to 2019, as well as the risks arising near these industrial zones.