Sealed Room

i have a sealed room with a window ac unit vented out away from the room. My issue is that when i seal the bottom of the door my main room ac vent stops blowing. When i remove the seal it blows again...... What is the problem here? It does not matter if i have the window running or not...the vent from the ceiling stops blowing if i completely seal the room....any ideads?

anyoneee please help

Your AC, does it have a switch to turn air exchange on and off. You want an AC that allows you to turn outside air exchange off. Once that's done, the AC will recirculate the air within the box.