if they do is it possible to take it apart and seal it? if some are and some arent what should a person look for. are there more than one type of window unit? if so what kinds... what about a in wall one at like a motel. do those exchange air outside?
They suck air from the inside...that's y there's a filter below the vents. Air goes through the filter, then the evaporator (where the air is chilled), then back out the vents into the room....
If you don't exchange the air, then you're heating and cooling the same air, basically accomplishing nothing. You can't add cold to make something warm. You have to remove the warm (loose interpretation of the first law of thermodynamics). You can buy some "personal air conditioner" units which do just that, but happen to blow hot air away from you, and cold air toward you, but they aren't very efficient. If you build a box around the backside of an inexpensive window unit, isolating the air space in back, from front, you can re-route the hose anywhere you like. Keep in mind you'll need a drain of some sort for the condensation to drip out of.
Window units do not pull in outside air. The indoor fan draws indoor air passes it over a cold coil and pushes it back into the room. The outdoor fan pulls outdoor air over a warm coil and blows it outside. The only time outside air is pulled in is if you have a small lever that opens a small damper that lets some outdoor air pull inside, but it lets only a small amount in. A hotel style unit has no outside air exchange at all - it is similar to a mini-split system. The outdoor and indoor unit are entirely separate. The other type of unit is a portable AC unit. A single hose unit pulls indoor air and blows hot air through a vent which you must vent outside your grow space, they are rather inefficient. A dual hose unit with both hoses run outside will pull in outside air and exhaust it back outside, no outside air is exchanged with indoor air.
The units that are larger then 18,000 btu's don't for sure, they move air over the heat exchanger and its cooled and then put back in the same room - on the outside the same thing happen only with the air outside - I was told this by the guy who I bought my new one from On smaller units, I had a 5,000btu one it would bow air outside, but now I have a LG 24,500 btu window unit and I know for sre its not doing that because before it used to smell outside, now it doesent not even if I go and smell close to the unit nothing - but before, wow did it ever smell