These tiny flies are not fruit flies. They are about the size of a Nat. They were coming in from a room in the basement. I fumigated the room but apparently it hasn't stopped them. I don't know what to do. Ive looked around the room for anything that they are attracted to. I can't find anything. What can I do and what are they? Is placing mint fragrance an option?

I periodically have a swarm of tiny unidentified flies in my lower level (split level on a slab). I have a couple of places in the concrete that are open, one being where the main waste line enters the slab and the cleanout is. But heck, they can get in just about anywhere. I get swarms of winged citronella ants too, that are huge. I try to find the center of the swarm and spray a little but mostly just wash the area with vinegar since I hate using chemicals. As long as they aren't termites or roaches, I don't get too upset (except under the toilet in the middle of the night). Since my entire lower level is on the slab I hang lavender sachets everywhere - bought a 5 pound box of lavender and hundreds of little pouches. Helps a lot and smells natural. I put them in drawers in cushions and boxes too.