The steam would condense back to water pretty quickly as it vented away from the actual fire or contacted a cooler surface. (If you watch the "steam" come from a tea kettle, you're actually looking tiny water droplets -- the steam is the invisible part between the kettle and what you can see.)
Also, even though water expands around 1000 times in volume when it turns to steam, the flow rates can't be all that high from a mist system. If you multiplied by 1000, I suspect you'd only reach a small fraction of the outflow valve capacity.