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

Several sulphur hexafluoride (SF6) tracer gas experiments were conducted in a subway system to empirical measure the possible pathways of toxic gas for subway tunnels and stations. A new mobile integrated measuring and analysis system was used, achieving high sample rates and a long measurement time. Due to the mobility of the sensor, tracer gas experiments were also carried out inside running subway coaches. All experiments showed a common pattern: The pathways of tracer gas dispersion often overlaps with escape routes, and these were contaminated within a few minutes. In case of catastrophic circumstances, like terrorist attacks or subway fires, some escape routes will became deathly traps, but the results also showed that others are safe. With the new sensor technique it will be possible to make safety assessments for escape routes in underground transportation facilities.