Tracer gas experiments in subways using an integrated measuring and analysis system for sulfur hexafluoride

Abstract. Several sulfur hexafluoride (SF₆) tracer gas experiments were conducted in a subway system to measure the possible pathways of toxic gas for subway tunnels and stations empirically. A new mobile integrated measuring and analysis system was used to achieve high sample rates and a long measurement time. Due to the mobility of the sensors, tracer gas experiments were also carried out inside running subway coaches. All experiments showed a common pattern: the pathways of tracer gas dispersion overlapped with some escape routes, which were contaminated within a few minutes. So in case of catastrophic circumstances like terrorist attacks or subway fires, some escape routes will become deathly traps, but the results also showed free escape routes. With the new sensor technique it will be possible to conduct safety assessments for escape routes in underground transportation facilities.