Yeah... they're supposed to have an external vent hose to dump the heated air outside of the area they're cooling. Really, without the vent tube, where is that heat supposed to go? I'd go beat the folks that created a system without an exhaust.
I recently (well... 2 years ago) visited the land of my birth.... specifically, the Oregon coast. One doesn't normally need AC in Pacific City, but there was a freakish June heat wave and we hit 90s. The hotel I was staying in had a portable unit properly installed with an external exhaust going outside. It did a great job for about 100sqft.
I've considered a redneck version of the design... where I put a small plenum on the back of a standard window AC unit and hook an exhaust fan and hose that runs outside. Seems ugly and ungainly. I'll keep that idea filed away for some drastic step in the future.