It's a big feature I've been working on for awhile. Luckily, it's finally finished! Ever since adding the "Needs" mechanics in the game I had this idea in mind and had started implementing it. Personally, I never liked the "Needs" mechanics. Actually that's why I made it an option. The ventilation mechanic isn't an option, it's now part of the game as I feel it add's to the realism.
You can't let air be stale in your grow rooms, so to counter act this you will need to have a ventilation system. If you don't have one you will be raided as soon as you start growing. Not only that, you will also need to keep replacing your filters. Once you hit level 30 you will unlock filters that will not need replacing but it does come at a price.
Unfortunately I ran out of time and wasn't able to do any bug fixes this update but I assure you that I will focus entirely on bug fixes in the next updates. I had to finish this feature before looking into bug's as I was too far into this feature to release an update without it finished.
I also wanted to thank everyone for your support for iGrow Game and keep an eye out for more updates very soon. Also if you have any problems or hit any bugs, please consider leaving your feedback in the forums as it will help me fix them if I know about them.
Happy Growing!
-iDev