These buildings did not have windows that opened, even though at the WTC, in some places they were blown out or broken for assorted reasons before the collapses. However, in all three buildings the mechanical floors did not have windows.

Also, all three buildings had elevator shafts, which create suitable enclosed spaces. In the Towers most of these elevator shafts were divided into three sections in order to prevent a chiminy effect. In a sense, they were like grain silos. In theTowers, you had the extra added convenience that in some of the freight elevators you could drive a fairly large truck right into them, so it wasn't hard to deliver the necessary materials to just the right place.

In WTC7, the 5th Floor had no windows and no tenents. I don't think it would have been that hard to close off certain spaces so they could overpressure them with vapor.

Yes, there were some fires visable in WTC7 but they weren't necessarily anywhere near the areas that were involved in the collapse.

can explain what I'm getting at better then I can? Apparently, I'm not the only one in the world that thinks a FAE weapon was at play here.

A Thermobarics Demolition Scenario

One can imagine a scenario in which a thermobaric devices were installed at each floor in the service core of each Tower. Each device would listen for a radio signal with a particular signature which would trigger a primary charge, dispersing the aerosol throughout its floor. Then, about five seconds later, a secondary charge would be triggered causing an explosion with overpressures sufficient to shatter the perimeter walls.

One advantage this theory has over most other explosives theories is that it avoids the need to install explosives near the Towers' perimeter columns. The thermobaric devices could have been installed entirely in discreetly accessed portions of the Towers' cores. The number of devices could also be much smaller -- perhaps just one per floor. The devices could have been encased in impact- and heat-resistant containers similar to those used to protect aircraft voice and data recorders, so as to prevent accidental detonation from the aircraft impacts and fires.

Other advantages of thermobarics include an absence of explosive residues, and much higher energy densities than conventional explosives. For example, whereas TNT yields 4.2 MJ/kg, hydrogen produces 120 MJ/kg (not counting the weight of the oxygen it uses to burn). 4

http://911research.wtc7.net/wtc/analysis/theories/thermobarics.html

in 1993.  

On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds (682 kg) of explosives was planted by Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 200 foot (30 m) hole through 5 sublevels of concrete leaving 50,000 workers and visitors gasping for air in the shafts of the 110 story towers.

 http://en.wikipedia.org/wiki/World_Trade_Center