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Astronauts take shelter after toxic leak alarm

Anatoly Zak, Spaceflight Correspondent
Jan 14, 2015, 20:54 UTC, Updated Jan 15, 2015, 8:40 UTC

Sen—A threat of toxic leak inside the International Space Station (ISS) forced the evacuation of the crew from the American-built part of the station into the Russian segment.

The alarm sounded onboard the station around 3 a.m. Houston Time Wednesday (9 a.m. UTC), indicating a potential release of ammonia coolant into the station's atmosphere, NASA said. The situation required the crew to don their gas masks, close the hatch in the Unity module separating the US and Russian sections of the ISS and take a shelter in the Russian segment, while mission controls in Houston and Moscow were evaluating the data.

After several hours of investigation, flight controllers in Houston concluded that the incident was most likely caused by a false alarm and no release of chemicals had taken place, NASA said. Still, the crew remained onboard the Russian segment for the most of the day out of an abundance of caution. Astronauts and cosmonauts from Expedition 42 reportedly used the opportunity to fix a joint meal onboard the Zvezda service module.

The hatch to the US part of the station was finally reopened at 2:05 p.m. Houston Time (8 p.m. UTC). Air samples taken by astronauts Terry Virts and Samantha Cristoforetti showed no traces of ammonia, NASA said.   

According to the chief of the Russian mission control, Maksim Matyushin, the safety of the crew was ensured thanks to cooperative and quick actions of cosmonauts and astronauts and support groups in Moscow and Houston.

The cooling system on the US segment uses liquid ammonia to remove excess heat from various components on board the outpost and radiate it into space. During the years of operation, the complex system proved to be maintenance-heavy and failure-prone and was a cause of several technical problems before, which required the intervention of the crew and even spacewalks.

However, US and Russian segments of the station have fully independent life-support and power-supply systems and can function autonomously. As a last resort, the six-member crew can board a pair of Soyuz spacecraft parked at the Russian segment and return to Earth as needed.