I have window-mounted air conditioners at my house. As you can see in the image at the top of this page http://en.wikipedia.org/wiki/Air_conditioner#Window_and_through-wall_units, air is retrieved from the outside and also from the inside. I know for a fact that some of the air from the outside also makes its way inside the house because I can sometimes smell it in the air of the air conditioner (for example, when there is a smoke smell outside the house).
My question is, do all air conditioners work with some air being taken from the outside and routed inside the house/building? Even for split system air conditioners (both for the home and building)? Or is this a feature that depends on the model, manufacturer, etc.?
No. Or at least they shouldn’t. The machine has a heat exchanger on the “room” side and draws warm air (from the room) over it. Heat is extracted from the air, which then gets blown out of another port; cooler than when it went in, obviously. The heat extracted from the room is transferred (via a fluid - the refrigerant) to the outside, and is then allowed to radiate off into the air through another heat exchanger (usually fitted with a fan to draw air over it). There should be no air flowing from inside to outside, or vice versa.
The only difference between a through-wall type and a split type is the distance travelled by the heat-transfer fluid.
The window type usually has a lever to switch between sucking in recirculated (room) air and fresh (outside) air. The lever operates a flap inside that divides the airflow accordingly. Usually the flap is covered with foam to make an airtight seal but the foam rots off over the years. With the foam gone, you can expect the recirculate mode to suck in at least some outside air.
This seems to make the most sense for what I experienced. We had a barbecue on our balcony. The place stunk up pretty fast so we decided to turn that particular AC unit off. That did the trick. The next day, the smell kept coming in from that AC unit. I asked my wife for some perfume and I went out and sprayed it on the area that sucks in air from the outside. The apartment ended up smelling great!
The unit is definitely sucking in air from the inside too. I’ll check the lever you mentioned. We live next to a mountain so there usually no problem with getting some air from the outside. Anyway, thanks for the information.