My apologies in advance if I oversimplify this.
When a T3 is filled and the coil assembly installed, the
tank is sealed except for the wick holes. The air tube runs down the middle of the
tank from the mouthpiece to the battery. There is a heating coil toward the bottom of the air tube and wicks coming from the tank. When you push the battery button and suck air through the air tube, a little bit of liquid in the wick is vaporized and goes up the tube into your mouth. Liquid moves from the tank through the wicks. When you stop drawing air, there is a slightly lower pressure in the tank, and air flows back through the wicks from outside the tank to replace the liquid that was used.
I hope I put that so it makes sense. This works pretty well as long as the coil isn’t gunked up and wicks are working right.
J.R.