Do they have to be vented out a window? Indeed. A transportable AC won't operate with no an exhaust hose. They should be vented to the outside mainly because they are extracting the new air that you would like released outside of the place. You can prefer to vent through https://docs.google.com/spreadsheets/d/1sFkX-195bzbspltn6kI7pJAwHC_IWJIWy0giWMghe84