Hey Guys, I'm not a physics student, not a physics lover but so admire those people that know physics!! Well thats why i come here for this question: what kind of air conditioner can help my room exchange fresh air? Does the Fan mode in every air conditioner intake fresh air or not? Here is the background: I have a very small bedroom (100-150 sq ft) with only one window (no central AC) in NYC. I desperately need a air conditioner for the summer but I'm worried about not being able to get fresh air whenever I want with only one window! I've did some research and knew that window-mounted air conditioner only circulates air in the room but not intake fresh air. Therefore I got a portable air conditioner knowing it will be easy for me to open the window -- but it turned out to be a disaster! Because portable air conditioner creates this huge negative air pressure in my room so the air is coming everywhere from under my door, any cracks in my window. The worst is since my living room is smelly (with cat litters and all the cooking smell), my room also sucks in all the smells and bad airs from the living room! As a result, I returned the portable air conditioner and knew that it is not going to work for me. So what kind of small windeow AC can I get to keep me cool and also provide me the option to exchange fresh air if i want? Is it possible? Does the Fan only mode intakes fresh air? I know i'm not going to die from running out of oxygen but I'm just so get used to having fresh air in my room. Thanks everyone! Hope my explanation is clear enough..