I'm sure they knew about the special sheathed construction of the towers. They probably also knew that the towers had been build to withstand the impact of a jet plane - and, at the time, it would not have been clear what size or type the planes that rammed the towers were. Add to that the fact that the towerrs were still standing after the impacts - aha! the towers were living up to specifications.

What nobody seems to have known or anticipated was that the fire would be so hot that the steel would melt. Again, nobody anticipated the collapses. It takes some expert from England to analyze the "obvious" and "inevitable" danger of collapse for us?

As much as they might have had refresher courses and had high-rise fighting training and known the peculiarities of all the major structures in the area, I don't think they or, apparently, any one except this professor in England had any clue it might collapse.

Isn't one aspect of firefighter training an emphesis to take no unnecessary risks? If you're dead, you can't help anyone. Of course firefighters take risks every time they answer an alarm. They take risks just driving down the street trying to get there, and horrendous risks in fighting the fires. But they're calculated risks, not suicidal risks. Or so I've been told.

I still believe they had no idea the towers would or could collapse. I've seen the videos of firefighters fighting ordinary fires in ordinary houses - when the thing is about to collapse, they do pull back, don't they?