NASA shut down ventilation aboard the International Space Station Monday and its astronauts donned surgical gloves and masks after a bad odor alerted them to a chemical leak, the agency said.

"The situation has stabilized and it has been reported back down by the crew that there were never any smoke in the cabin, however there was a smell associated with KOH (potassium hydroxide)," American ISS manager Mike Suffredini told reporters here.

"It's an irritant, it's not a life-threatening material, and at no time did the crew have to put on the gas mask or the oxygen mask," he said.

"However we did have them wearing some surgical gloves and masks," he said.

"Part of the procedure when you get a smoke or a potential fire indication, (is that) we activate the emergency system and that shuts down all the ventilation in the vehicle to keep us from spreading whatever the smoke or toxic spill is," Suffredini said.

The crew initially reported light smoke and an odor of potassium hydroxide coming out of an oxygen vent on the Russian section of the space lab, he said.

"There is no more smoke, just a smell, the situation is stable," ISS astronaut Jeff Williams of the United States told mission control, in an update retransmitted on NASA TV.

"There is no more emission, the CO2 isn't increasing … and everything is good," added Pavel Vinogradov, the Russian commander of the orbiting space lab.

NASA is now cleaning up the odor, reconfiguring the ventilation system and taking readings for levels of carbon dioxide (CO2) and hydrogen cyanide (HCN) on the ISS, Suffredini said.

"All of them are well below any limits we worry about," he said.

"The crew is doing very well. We don't quite know exactly the nature of the spill and we have plenty of time to work it out," he added.

The incident will not delay the docking, scheduled for Wednesday, of the Russian Soyuz rocket that left Kazakhstan earlier Monday, carrying Iranian-born US citizen and millionaire tourist Anousheh Ansari, NASA's Michael Lopez-Alegria and Russian cosmonaut Mikhail Tyurin, toward the ISS.

"The crew is doing very well in the Soyuz," Suffredini said.

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