How to create fog in one specific area of a scene rather than using volume scatter to effect whole scene

Question

Title is self explanatory. Indoor scene where you can see the outside. Fog to be illuminated by streetlights.

Answer 1

Instead of editing the world to have scatter volume, you can just create a mesh and place it wherever you want, then remove the surface node, and add Volume Scatter to the volume. Then adjust the Density as you want.

Hope this helps.