I had an infestation of some little black flies in the room. Kind of like tiny fruit flies. They bred in the soil. I foolishly introduced them by bringing in some soil from outdoors.
I kept their numbers down by using soap spray and hanging strips of yellow card smeared with oil to trap them. I also encouraged spiders to catch them. Eventually they just died out themselves in the summer when it got too dry for them.
Best thing for indoors is don`t introduce any critters then you`ll be fine.
