“There is a rather unpleasant odour, which travellers have complained about. We acknowledge that there is a problem and will be trying to find out what's at the bottom of it in the next few days,” Wiener Linien spokesman Daniel Amann told Radio Vienna. He added that the smell is not sulphurous - like the notoriously stinky Stephansplatz station in Vienna's 1st district, but "smells more like canal".
Wiener Linien staff will use a special camera to examine the pipes during the night, when the U1 line isn't operating. "The station building is quite large, and has a lot of drainpipes. We'll be examining these to find out if there's a leak,” Amann said. A special camera has been ordered, similar to the cameras used by doctors for endoscopic surgery. The camera is connected by a cable to a monitor, so that staff can follow the progress of the camera as it is pushed through the pipes.
Locals and visitors often complain about a persistent nasty smell at Stephansplatz. This is because when the station next to St Stephen's Cathedral was constructed an organic soil hardening agent was injected into the ground to prevent the soil from subsiding and damaging the foundations of the famous cathedral. However, once in the soil the hardening agent undergoes a chemical reaction involving sulphur compounds. Which is why the Stephansplatz U-Bahn station often smells like rotting eggs, and worse.