Fresh Air

So I have two plants going at the moment in Veg, one 2 weeks old another 1 week. I was wondering if it would be enough fresh air for them if I leave a window jarred open? No direct intake...

That will work, but when they get larger they may need more CO2. There are many ways to get good air to them. Most people use electricity to vent good air to them, while some mix up solutions to generate CO2. If you get to the point of needing better ventilation try going a route that will be great for expanding your room size or adding more plants. The old saying: "Do it right the first time." Will save you time, money and work. Good Luck!

Well I'm in the room with them most of the day and my bro sleeps next door to them (bathroom in the middle) So it's Co2 I need more of not Oxygen for the roots? or both? lol

The whole "fresh air" thing is bullshit unless the space is sealed up. The highest amount of Co2 is in places lived in with no fresh air. Co2 is heavy so it sinks the the lowest possible place which is usually the basement. A basement is better than a room with a bunch of fresh air. The Co2 in a basement is 30% more than outside.