Here's what demolition experts use in steel framed buildings, the linear shaped charge ... It generates around 3,000,000 psi pressure ... at a speed in excess of 27,000 feet per second ... There are over 1000 different types of explosive ... With the use of delays we can control ... where the debris lands ... vibration ... noise level. WMV video download (680kB) The job of a shaped charge is to cut steel H-beams. "The way we do this is by cutting the beam at an angle which through a series of beams cut at the same angle will tend to make the building shift over and 'walk'" WMV video download (670kB) The photograph below demonstrates that the WTC beams were not cut by welders. Because of fuel and time constraints welders would have used a cutting torch to cut the shortest distance possible - straight across the beams. Also, cutting torches cut by forced oxidation, therefore the large amount of once liquid metal congealed on the beam would not be present. If a "progressive collapse" is required the beams are cut at opposite angles: Compare the audio in the following video clips: Demonstration of a linear shaped charge.

WMV video download (391kB) WTC firefighters shocked by a loud explosion.

WMV video download (306kB) The linear shaped charge demonstrates the sound made by high velocity explosives. The sound which shocked the firefighters is all but identical, thus indicating it was created by a high velocity explosive detonation. Why were high velocity explosives detonating in the vicinity of the World Trade Center?