out of the subways would increase. >> but measurements of air flow in the escalator area show this would not effect a small fire on the steps. multiple layers of paint on the ceiling. >> when they did some tests, when the agencies did some tests on the ceiling paint, some of it that was not damaged, they couldn't make the flames spread fast enough along it. and that's when they started to question what else could be the main fuel? that's when they came to talk to us to see if we could do anything to help. >> what do you think of these results? >> investigators now turn to a team of forensic mathematicians at the investigative firm of cfx. their goal was to create a computer simulation of the deadly fire using computation fluid dynamics or cfd. this was the first time it would be applied to the behavior of fire.