The Ground Zero Fires Were Not Conventional Fires

Here is a photograph showing the fires in the twin towers on 9/11:

The smoke rising from the towers is dark in color because it contains soot.

The smoke released by any type of fire (forest, brush, crop, structure, tires, or waste) is a mixture of particles and chemicals produced by incomplete burning of carbon-containing materials. All smoke contains particulate matter (PM or soot). Dark smoke implies the presence of soot. Soot is produced when a fire is oxygen starved, or has just been extinguished. Soot also has a high thermal capacity and may act to rob a fire of heat by carrying it away.

Here is a photograph showing Ground Zero following the collapses:

The fires at Ground Zero were oxygen starved, so the color of the smoke should be very dark. As you can see, this is not the case - the smoke is white.

Also, the oxygen starved fires should have been relatively cool and easy to extinguish. This was not the case:

The Ground Zero fires were not conventional fires.

Probable cause: thermite.