thats what ive found, when you introduce CO2 directly, it changes things somewhat. some guys dont realize how important CO2 introduction is either. i introduce CO2 up high ( its heavier than air) and i have it setup above sort of a "dissipation" setup i made so it distributes somewhat evenly. one time i had some plants veggin and i left for a few days. unbenounced to me, one of my CO2 connections came loose and one plant got an extra dose for a few days. it grew about 3" more than the other ones in the room...LOL

i never have had any issues with bug or mould myself. i keep the air circulating pretty well also.