How do I fill a room with mist (smoke) in blender cycles? I'm trying to fill a room with humid mist, and cannot get the smoke domain to change from grey to any color. I also tried to just use volume scatter within the world nodes and it requires too much ram for my computer. Any advice on just making really minor, atmospheric mist?

Here's my new node setup. It works, but cannot get the color to change from grey to transparent white. Any ideas?
Add a big cube that surrounds the room (there is no need to set it as domain of a smoke simulation) and use a Volume Scatter node connected to the Volume output of the Material output Node. Unplug anything that is connected to the surface socket.



like in this example:



and this post: 

Low lying fog bounding object rendering as solid