Originally Posted by
livedarklions
Yeah, I should have been clearer that I meant foam in a figurative sense, not literal or technical--all I meant was that the protective mechanism is still at least in part an air space collapsing.
In the case of the WaveCell, you should think of that space just as clearance space between plastic members. It also happens to provide ventilation space. (There is no air compression going on in the WaveCell portion of the helmet.)
-mr. bill