Australia to use harmless gas to track potential attack routes

Small amounts of a non-toxic gas will be pumped through Melbourne, Australia's underground railway stations next week as part of preparations in the event of a fire, gas leak or terrorist attack.
On Wednesday and Thursday of next week, the Department of Transport will work with the fire brigade and other emergency agencies to release sulphur hexafluoride into the three City Loop stations – Flagstaff, Melbourne Central and Parliament, The Age reports.
Releasing the odorless gas into the air flows will allow the federal government, the fire brigade and local rail authorities to know how oxygen and other gases disperse in the tunnels. Staff with ambient air analyzers will then take samples around the station to model what the gas does when it is released.
According to the Department of Transport, there are no health or safety risks to the public from the gas release, which would last for approximately three hours on both days, starting at 2 p.m.

Stephen Lincoln of Adelaide University's School of Chemistry and Physics said that sulphur hexafluoride is harmless if used in the low quantities planned next week.
"They use it quite extensively in the London Underground and also in the New York subway [for air quality tests]," Lincoln said, according to The Age. "It is a very unreactive gas, and it therefore is not injurious if you ingest it. It's not much absorbed into the bloodstream."
Chris Watt, the fire brigade's assistant chief office, said that approximately 30 firemen would be in the loop during testing.
"The whole purpose of the trial is to study where the sulphur hexafluoride travels to," Watt said, according to The Age. '"We want to understand potential areas of risk if a chemical or biological release occurred in an underground transport system."
Signs that alert passengers to next week's trials will be put up today at Melbourne Central station, which is where the gas will be released in the trial.