Astronauts on the International Space Station made a daring walk in open space on Friday to repair an ammonia leak on an external cooling station. According to a report from Discovery News, one of the crewmembers sustained minor damage to his gloves during the repair mission, but the two astronauts were otherwise unharmed.

Ammonia is used as a coolant on the space station, but can cause serious damage to the astronauts’ health if flakes make their way inside the station. The crew received extensive training in decontamination procedures, and the two spacewalkers were able to successfully prevent any harm to the staff working on the station.

NASA astronauts Kjell Lindgren and Scott Kelly carried out a 6.5-hour spacewalk to repair the station’s cooling system, but this isn’t the first time they have faced the risk of ammonia contamination. Three years prior, a similar leak occurred and required an entire new pump to fix the damage. The makeshift rig built by astronauts to set the new pump in place has remained on the outside of the space station to this day, and Friday’s mission was relatively quick as a result.

Kelly and Lindgren reported that there were icy ammonia flakes chipping off from the work site and floating away into space as they open and shut the valves on the pump. In previous instances where ammonia was leaking from the space station’s coolant system, astronauts were instructed to wait outside of the station until the traces of ammonia were sublimated away by the sun. After sufficient time had passed for the contamination level to drop off, the astronauts were allowed to return to the work site.

Kelly reported that some of the stitching on one of his gloves had come loose during the mission, with a loop of thread popping up out of the material. Subsequent inspection was carried out and mission control confirmed that Kelly was at no threat of exposure to ammonia or harmful radiation from space.

The astronauts also spent the time working on lubricating the space station’s robotic arm, and other basic maintenance tasks.

Kelly has been in the space station for almost 225 days, breaking all previous NASA records for longest time spent in near-earth orbit. He landed on the station in March 2014, and won’t be leaving until March of 2016. He is joined by the Russian cosmonaut Mikhail Kornienko, who is undergoing a year-long experiment that seeks to determine the effects of long space flights on the body.