WTC1 10:18am pressure pulse

for full time see WTC1 Fire Progression 2x speed series:
http://www.youtube.com/watch?v=k_gdWmYaFVc http://www.youtube.com/watch?v=1rzUWd3IzBk rel=”nofollow”>http://www.youtube.com/watch?v=2Dvftx9fawQ http://www.youtube.com/watch?v=8Xs2Bgmust4 http://www.youtube.com/watch?v=xz6ulS18bc0

10:18 a.m. to Collapse of WTC 1 at 10:28:22 a.m.

“By shortly after 10:18 a.m., the fire spreading toward the west on the north side of the 92nd floor was approaching the edge of the face. Despite the presence of flames over a significant length of the floor, the fire appeared to be burning with a low intensity at separated locations, with essentially no smoke coming from nearby open windows. An event took place within the tower at 10:18:48 a.m. that generated a pressure pulse with sufficient magnitude to force a large amount of smoke from the open windows on the 92nd floor, along with smaller amounts from open windows on other floors on the north face and on the other faces of the tower. While it seemed likely that the pressure pulse was generated by some sort of collapse within the tower, e.g., a portion of the core settling or a partial floor collapse, it has not been possible to determine the nature of the event or even its general location based on the visual record.”
– NIST NCSTAR 1-5 p17