Biting gnats in Georgia

[Michaela G.]

So, I have an apartment and 2 months ago there were suddenly biting gnats appearing. We have no idea how they originate. For a month the tenant tried to deal with them herself, put her plants outside, wiped down the aparment. Apple cider vinegar everywhere, beach down the drain. She got lots of bites. 

My exterminator has been there 3 times now and has to come back tomorrow again. I may have to put my tenant up in a hotel. We don't know where they came from and nothing seems to eliminate them. 

Has anyone ever dealt with that? This is in Atlanta