Hazardous Gas Dispersion in Tunnels: Full-Scale Experiments within the CHEMATUN Project

Abstract Tunnel safety research has traditionally focused on fire scenarios, while incidents involving hazardous chemical releases remain comparatively under-researched, despite being governed by different physical processes and emergency-response objectives. The CHEMATUN project addresses this gap by combining full-scale gas-release experiments with the development of a computational fluid dynamics (CFD) framework for hazardous gas dispersion in tunnels. This contribution reports a progressive full-scale experimental programme at the Zentrum am Berg research facility, comprising preliminary tests with carbon dioxide and helium in the Southern Road Tunnel and two main series in the Northern Road Tunnel. Carbon dioxide and helium releases were investigated under still-air and longitudinal ventilation conditions. Furthermore, hydrogen releases were investigated under longitudinal ventilation, and carbon dioxide was additionally tested under semi-transverse ventilation. The results indicate that gas properties govern the fundamental buoyancy-driven dispersion regime, while ventilation state and strategy strongly influence the transport, direction, and persistence of the resulting gas cloud. The findings highlight the need for ventilation strategies tailored to the specific hazard and provide a full-scale experimental basis for the subsequent development and validation of CFD models for additional release and ventilation scenarios.