The concrete floors were relatively thin. Maybe 4" thick. The billows/clouds of stuuf taht followed the collapse--recall the video of a guy running away from the white-ish cloud that came after the collapse--was concrete turned into the size of dust particles. The streets were layered with it to a depth of 2 to 3". That dust is suspected to have contributed to or caused the deaths (post 9/11) of about 100 firefighters and other people who were on the scene and not wearing breathing apparatus. They got it in their lungs and contracted 'things' that killed them within a few years, (It is established SOP for firefighters where I am to wear breathing apparatus even after the fire is extinguished because in the aftermath/recovery phase, the burnt structure will keep releasing potentially dangerous gasses and toxins for about 72 hours. Obviously the most dangerous time is during the fire itself and the few hours after it extinguishment.

I am not faulting anyone. The combined weight of bunker gear (the jacket and pants and boots and lid that you see firefighters wear to help protect them from heat and flame) is about 50 pounds. Add another 20 pounds to that for a BA tank and face mask and that guy or gal is carring another 70 pounds in addition to his or her body weight. So, anywhere from 20 to 50% more than the firefighter's 'naked' body weight. That does not yet take into account the clothing the firefighters is wearing under the bunker (turnout) gear. A half hour of that additional weight combined with heavy exertion doing whatever at the fire scene can cause very physically fit young guys (and old guys) to need, big time, ten to fifteen minutes of recouperation time to rest and rehydrate. Some big scenes require that kind of work for hours at a time, so departments rotate ffs in and out of the actual attack scene. If they don't the biggest killer of firefighters (heart attack) will take someone within 48 hours. So, the urge to remove the tanks and jacket (lightens the load by 30 pounds or so) is real and almost irrestable. (Trust me on that one.)

Maybe that type of pulverization is common when large structures collapse. I have never encountered it at scenes. Spalling, flaking, cracking--yes. Concrete being turned into fine dust, no.

That is what prompts my question.