As Cym Lady points out, those little bugs are just annoying without causing harm.
I have lots unfortunately. They came in on some potted houseplants.
They seem to go dormant during the summer as I don't see any. then as soon as the weather gets cooler, they come back.
I tried a few things, but didn't get rid of them all. so I just live with them now. lol
I tried the yellow sticker thing, but my fungus gnats must be color blind.
Drying the pot doesn't work becase you may end up killing orchids before gnats. They are not that sensitive to drying as some literature says they are. and you already found out yourself that this doesn't work.
I do kill every single thing I find. with my hands.
You hear clapping of hands quite often.
Considerig the fact that each female can lay hundreds of eggs, killing every single one you find manually really adds up I think. When I see rather fat one, meaning loaded with eggs, I make sure it is dead all the way.
If you have just a few pots, then CO2 chamber might work. but dryice can chill your orchids as well as the bugs.
A warning about using the cinnamon extract, I used it last spring on a few of my flowering orchids.
Well, all the flowers were dropped within a couple of days after the application. no damage done on the leaves, so make sure you don't spray the solution on any flowers as you risk losing them or severly browning them.
Cinnamon extracts are found at spice section at supermarkets by the way.