Thermal plants are the core of heating systems, converting the chemical energy of fuels into thermal energy. Maximizing efficiency is crucial. This training module examined thermal plants using liquid and gaseous fuels, with a focus on heat generators and heat exchangers, circulation pumps, and safety devices. Heat generators, heat exchangers, pumps, and safety aspects were explored in detail. Regulations governing gas- and liquid-fired thermal plants were discussed, along with fire prevention and safety compliance for hot water thermal systems, based on the INAIL R 2009 Collection (formerly ISPESL). An essential resource for professionals in the field.