I AM using air freshener, as a matter of fact. Two of them, for a fairly small room, and there's still flies coming in as soon as I open the window!
To be fair, there would usually be a lot more of them in here, so I think the lavender must be doing somehting. The ones that are in here are also smaller than usual (although that might have something to do with the recent rainstorms?) and seem a bit slow and sleepy rather than buzzing around as energetically as normal. They also stay in the half of the room closest to the window rather than flying all the way in as they normally do, and I assume that must have something to do with the air freshenersbeing in the middle of the room. But to stop them flying in completely I'd need to completely saturate the room in lavender smell and that's impossible however many air fresheners I use because I have the window open!