Imagine a closed room with holes on the floor. Through some trigger, a trap is activated in which the holes begin to suck air from the room (say to some other chamber), so that the chamber is becoming more and more like a vacuum.
Suppose an average human being was placed into this chamber and triggered the trap. What would happen to him? Obviously he would die, some way or another (suffocation?) but what are the stages? How long could he last?