air con query

[deggers316]

i have an air con unit which as advised is more or less in a sealed room (air wise) the outlet pipe is well sealed too, so when the unit is cooling air is drawn from the room over the coolers and blown back out into the room ,but the bottom half of the unit also pulls air from the room and out of the pipe through the window when cooling is in operation to pass over the heated gas pipes,
so where does this air come from if the room is sealed as much as possible to make the air con more efficient ? it is noticeably harder to close the door when going out of the room when cooling is in operation as it trying to pull air in to pass over the heated gas pipes and through the window if the room is supposed to be sealed how can it do that without leaving the door slightly ajar

[buildersmate]

One needs a bit of new air rather than 100% recirculated. I imagine this new air is supposed to come from within the rest of the building - through the door. The negative pressure differential is maintained to minimise the amount of cooled (AC) air escaping into the rest of the building.