Here's an interesting revelation

The debris from the collapses of the WTC towers also initiated fires in surrounding buildings, including WTC 4, 5, 6, and 7; 90 West Street; and 130 Cedar Street. Many of the buildings suffered severe fire damage but remained standing. However, two steel-framed structures experienced fire-induced collapse. WTC 7 collapsed completely after burning unchecked for approxiamately 7 hours, and a partial collapse occurred in an interior section of WTC 5. Studies of WTC 7 indicate that the collapse began in the lower stories, either through failure of major load transfer members located above an electrical substation structure or in columns in the stories above the transfer structure. The collapse of WTC 7 caused damage to the Verizon building and 30 West Broadway. The partial collapse of WTC 5 was not initiated by debris and is possibly a result of fire-induced connection failures. The collapse of these structures is particularly significant in that, prior to these events, no protected steel-frame structure, the most common form of large commercial construction in the United States, had ever experienced a fire-induced collapse. Thus, these events may highlight new building vulnerabilities, not previously believed to exist.

but also we were pretty sure that 7 World Trade Center would collapse. Early on, we saw a bulge in the southwest corner between floors 10 and 13, and we had put a transit on that and we were pretty sure she was going to collapse. You actually could see there was a visible bulge, it ran up about three floors. It came down about 5 o’clock in the afternoon, but by about 2 o’clock in the afternoon we realized this thing was going to collapse.

I don’t know how long this was going on, but I remember standing there looking over at building 7 and realizing that a big chunk of the lower floors had been taken out on the Vesey Street side.

From there, we looked out at 7 World Trade Center again. .... but at the edge of the south face you could see that it was very heavily damaged.

We were told to go to Greenwich and Vesey and see what’s going on. So we go there and on the north and east side of 7 it didn’t look like there was any damage at all, but then you looked on the south side of 7 there had to be a hole 20 stories tall in the building, with fire on several floors. Debris was falling down on the building and it didn’t look good.

Boyle: There was a huge gaping hole and it was scattered throughout there. It was a huge hole. I would say it was probably about a third of it, right in the middle of it. And so after Visconti came down and said nobody goes in 7, we said all right, we’ll head back to the command post. We lost touch with him. I never saw him again that day.

One Battalion Chief coming from the building indicated that they had searched floors 1 through 9 and found that the building was clear.390 In the process of the search, the Battalion Chief met the building’s Fire Safety Director and Deputy Fire Safety Director on the ninth floor. The Fire Safety Director reported
that the building’s floors had been cleared from the top down. By this time, the Chief Officer responsible for WTC 7 reassessed the building again and determined that fires were burning on the following floors:
6, 7, 8, 17, 21, and 30.391 No accurate time is available for these actions during the WTC 7 operations; however, the sequence of event indicates that it occurred during a time period from 12:30 p.m. to
approximately 2:00 p.m.

The Chief Officer then met with his command officer to discuss the building’s condition and FDNY’s capabilities for controlling the building fires. A Deputy Chief who had just returned from inside the
building reported that he had conducted an inspection up to the 7th or 8th floor.392 He indicated that the stairway was filling with smoke and that there was a lot of fire inside the building. The chiefs discussed the situation and the following conditions were identified:

• The building had sustained damage from debris falling into the building, and they were not sure about the structural stability of the building.

• The building had large fires burning on at least six floors. Any one of these six fires would have been considered a large incident during normal FDNY operations.

• There was no water immediately available for fighting the fires.

• They didn’t have equipment, hose, standpipe kits, tools, and enough handie talkies for conducting operations inside the building.

At approximately, 2:30 p.m., FDNY officers decided to completely abandon WTC 7, and the final order was given to evacuate the site around the building. 395, 396 The order terminated the ongoing rescue
operations at WTC 6 and on the rubble pile of WTC 1. Firefighters and other emergency responders were withdrawn from the WTC 7 area, and the building continued to burn. At approximately 5:20 p.m., some three hours after WTC 7 was abandoned the building experienced a catastrophic failure and collapsed.

In May 2002, the Federal Emergency Management Agency of the United States (FEMA) released a report on the collapse. FEMA made preliminary findings that the collapse was due primarily to fires on multiple stories caused by debris from the other two towers, and not to the actual impact damage of 1 WTC and 2 WTC as they collapsed.

The report noted that prior to this collapse there was little, if any, record of the fire-induced collapse of a large fire-protected steel building such as 7 WTC.