"Portable air conditioners (PAC) work normally the same way as built-in air conditioning, sucking in warm and humid air, cooling and dehumidifying it and return it back into the room. Single duct models, with a duct connected to a window to vent heat from the small place, can be very effective at cooling most of the small place, but they draw the air from the room in order to cool it and vent some of it outside of the room. Venting the hot air outside through the duct results in a net air pressure reduction, so more warm air is drawn into the room from the rest of the places. The portable air conditioner thus faces a continual struggle to cool the particular place or room. Portable air conditioners units are a little noisier indoors than most split-systems, which have the advantage of having the noisiest component, the compressor, situated outside. The heat extracted to or from the air is vented through an air duct system that we can install in an open window. This system also condenses water from the air while cooling, collecting this in a draining or tank, it goes via a tube. Dryer air feels more comfortable and enhances the cooling effect. "