The ammonia, which is used as a space station coolant, can be highly toxic if flakes of the substance are accidentally carried into the space station. Fortunately, tried and tested decontamination procedures worked like a charm and the spacewalkers, nor the rest of the crew,were in any danger. The same procedure will be used today before the astronauts return to the interior.
NASA astronauts Kjell Lindgren and Scott Kelly were 2 hours into a planned 6.5 hour spacewalk to carry out maintenance work on the station’s coolant system. Three years ago, the space station crew were faced with carrying out an emergency spacewalk to stop an ammonia leak. An immediate jury-rigging solution was put in place, and eventually new pump was installed. However, the jury rigging had remained in place to this day, so one of Friday’s spacewalking tasks was to remove the quick leak fix.
http://news.discovery.com/space/spacewalkers-safe-after-toxic-ammonia-leak-encounter-151106.htm