hmm...they told me it was sealed bro, Im going with a mini split but only because they dont make a portable unit big enough for my needs.Sealed is definetly the way to go, otherwise your venting co2 out of the room costing you money not to mention the odor.It says right in the description that one hose is the condenser intake and the other is the condenser exaust, I think the only way it will leak air out of the room is through the hose connections on the unit.If you caulked them im pretty sure it will not create negative pressure, how can it?