Hot rivets don't have to fall from a skyscraper to cause a lot of commotion. A friend in Chicagowas going to a HS Basketball Game. Part of the trip was under the 63rd St. El. A workman missed a hot rivet and it went thru the roof of his car (Cloth in those days)and between two boys in the back seat,setting their coats on fire, burned thru the seat cushion and set the car on fire.
By the time Jack figured out that something was wrong and stopped the workmen who were running along the tracks above him had alerted helpers on the street below. They helped put out the fire.
The El bought new coats and repaired the car.