A slow leak was tracked down to a cracked tube that helps keep window glass mist-free in the US-built module, Destiny. The module was sealed for about two days while the astronauts were looking for other possible leaks.
Crew commander Michael Foale tracked down the leak on January 11 with a portable ultrasonic device. The next day the commander and Russian cosmonaut Aleksandr Kaleri removed the faulty tube and sealed the place.
Russia's Progress Mi-11 spacecraft will bring a new tube to the ISS. It is due to be launched from Baikonur, the launching site Russia rents from Kazakhstan, on January 29. Air pressure has stabilized on the station by now.
Air pressure dropped approximately 1mm of mercury a day before the leak was identified, which was far above the critical rate. Although the station's air reserves were enough for more than 180 days, by identifying the leak the astronauts clarified their further actions.