Because on the FCOM 1.21.10 P6 reports (as written before) during take off the RAM AIR inlet and outlet close both of them. So i'm wondering where the air should come in...
Bio161,
RAM air enters the aircraft before takeoff and definitely both the RAM air inlet and outlet valves (as well as the outflow) stay closed fot takeoff. Though the valves (and packs) have remained open while the pre-daperture checks and taxi-out phase, so that a pressure slightly higher than outside has built up inside the cabin: when the valves automatically close for takeoff (TO phase), this slighlty higher pressure remains trapped into the a/c, allowing the so called "cabin pre-pressurization". This way of building up pressure prevents a surge from occurring upon the selection of PACKS, then increasing the cabin comfort.
fredgrav