Unprecedented No-see-um infestation in Upper Peninsula of Michigan
We are summer residents in a well-built house. This is our 25th year near Chatham in the Upper Peninsula, and we are being driven out by a plague-sized infestation of no-see-ums. We vacuum the entire circumference of our bedroom ceiling -- where the ceiling meets the wall -- multiple times a day. This is where they congregate, though not so in any other room in the house. We keep the windows closed in that room knowing they can come through screens, but it makes no difference. We use sticky traps and have ordered an electric indoor mosquito catcher. I am covered with weeping sores.
Without an in-person inspection, I cannot offer any clue as to why only a single room would be involved. Do you see the flies in quantity anywhere outside of the home? Perhaps you are dealing with some different form of tiny fly that has a different origin than would be expected.
You might consider sleeping in a different room for a while or getting a mosquito net system to place over your bed. Since the flies are siting on the wall/ceiling area, a daily spray of an indoor ant/bug/roach killer product where the ceiling and wall meet would likely kill many of them by their contact with the sprayed surface. It might have a bit of an odor, but if used this way you will not have significant contact with the product. Spray in the morning or afternoon so there is time for the odor to dissipate a bit before you use the room.