Russian astronauts reported smoke and a burning smell in their main compartment yesterday.
There wasn't enough smoke to activate the alarms or to warrant the use of masks by the six-man crew. The smoke came from a vent and dissipated within a half hour or so.
Commander Steven Swanson says there was only a small amount of smoke and everyone was fine.
The astronauts quickly disconnected the electric water-heating unit and activated air purifiers in the Zvezda compartment, Russian for star.
Today, the astronauts installed a spare unit. NASA says it's working normally.
The astronauts say they didn't see anything unusual with the removed device.