|What are firewalls? What are they made of? — RB
Firewalls are just insulating, non-flammable walls that prevent the heat from a fire on one side of a firewall from initiating combustion on the other side. As far as I know, most firewalls are made from masonry block. Ceramics such as stone or cement are already fully oxidized and can't burn. Furthermore, most ceramics are poor conductors of heat and many can become almost white hot without melting. As long as a masonry wall is thick enough and sturdy enough, it can tolerate having a fire on one side without conveying that fire's heat to the combustible materials on its other side. If there aren't any holes or flaws in the firewall, it will prevent the spread of fire between adjacent buildings.