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Originally Posted by BigDon
Irish, so what happens in case of fire? I'm sure that has been planned for. Not necessarily void and replace, but what's the plan for a smokey fire? I know stuff doesn't burn well in micro gravity but that just makes it smokier. (that last word doesn't look right)
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There are several options, but first it's important to understand how the ISS fire detection and suppression system works.
A fire can be detected by the crew or by a series of smoke detectors throughout the ISS. If a smoke detector sees smoke in a given module, the Command & Control computer shuts down intermodulation ventilation (IMV) and intramodule ventilation for that module and that module only. This prevents the fire from being fueled by fresh oxygen and prevents contaminated atmosphere from being spread throughout the station.
A crew annnunciated fire response is slightly different in that it shuts down IMV across the ISS but allows the intramodule ventilation to continue. The logic behind this is that the crew may annunciate the fire response in a module other than the one there's a fire in (fair enough - you won't want to hang around to pull the fire alarm either!). Because the fire might not be pronounced and the crew may react having only smelled smoke, the intramodule ventilation stays running to determine where in the ISS the fire is. Remember, without gravity the smoke will simply billow outwards from it's source rather than rising to the ceiling like it does on Earth - without air being forced past the smoke detectors they won't work.
Basically this all means that fires and fire byproducts will be isolated to parts of the station. If the severity of the fire warrants it, the module can be sealed off (well, some) from the rest and vented to space. More than likely, however, the IMV will simply be reestablished so that filtering units can do there work. Air is a commodity up there so they don't vent it overboard if they don't have to.
If the fire is bad, and I mean REALLY bad, the crew will simply close the hatch to the burning module, turn off all the equipment in it (remotely), and wait. Of course when they close hatches they make sure to remain on the side of the hatch that permits their escape via Soyuz or Shuttle!