This thesis analyses safety management in tunnel excavation, focusing on the challenges posed by methane in underground works. After reviewing the Italian and European regulatory framework, including Legislative Decree 81/08, ATEX directives, and interregional guidelines, the study examines how these provisions are applied in practice. The Val Lemme window, part of the Terzo Valico dei Giovi high-speed railway project, serves as a case study. Detailed attention is given to methane risk assessment, tunnel classification, monitoring systems, and operational safety procedures, including the exceptional use of non-ATEX equipment. Moreover, specific case studies illustrate the practical application of these procedures, highlighting how construction activities were adapted to balance work continuity with the protection of workers in high-risk environments.