body area 114 by a hand 302 the barrier flap 300 that can arc and hinge remains in the u201c closed u201d position forming a circumferential seal around the inner circumference of the neck although the container 100 is being held inverted by the hand 302 the body area 114 is not yet being significantly squeezed with the barrier flap in the u201c closed u201d position and the circumferential seal engaged any fluid or gas exchange between the inside and outside of the container is prevented fig5 shows an inverted container 100 that is being squeezed at the container 39 s body area 114 by the hand 302 while the container 39 s body area 114 is being squeezed internal container pressure significantly increases exerting force on the barrier flap 300 this internal pressure causes the barrier flap 300 to exert increased force against the resistance stop 112 as the container continues to be squeezed the internal container pressure continues to build until the pressure causes the barrier flap 300 to overcome the obstructive force of the resistance stop 112 when the barrier flap 300 overcomes the obstructive force of the resistance stop the barrier flap hinges to the u201c open u201d position simultaneously the barrier flap 39 s movement away from the circumferential sealing region 108 causes the circumferential seal to break and become disengaged the barrier flap continues to move towards its u201c open u201d position about its hinging region 304 until it comes to rest along the inner neck wall 104 after the container is inverted and once the circumferential seal is disengaged gravitational forces.