I agree that you probably could use some more fresh air. Also try not watering it so much, maybe let it get on the "dry" side before watering. It will show the tips of the leaves burnt, or a curling/twisting of the leaves
I'm growing outdoor I can't control the Co2. There's no burnt leaves and I think I saw 1 or 2 little leaves that's curl up but it rained for 2 days and if there's any kinda lock it should be flush out already and I had to water my plants because it was over 100 degrees.