Hey guys,
I know Im a bit late replying on your gnat problem but I think I found a fairly harmless treatment.
I have regular plants just inside my balcony and I found lots of them. They spread to just about all of the plants.
I really noticed the problem when I decided to re-pot some of them.
What I did was, I went to the shop and bought camolime tea, put a teabag in a pot and poured 2 litres (4 pints) of boiling water on it.
I let it sit for the night to let the teabag do its thing. It also removed the chlorine in the water.
Just give the plants a good soaking and see how they get on. My plants are gnat free already with only one flush and are doing fine.
I read somewhere about this before Im sure. I think the camomile doesnt kill the gnats directly. It just makes their food inaccessible to them thus starving them.
Give it a try if you want sometime. It worked for me.
I havent had to use it in the G room yet but Im sure it would work and there will be no nasty chemicals being used.

Let me know if anyone tries it.

Take care boys and girls