I recently was sent to inspect a Hot Water Tank which was damaged by a fire in a duplex in Beechview section of Pittsburgh
Now amazingly the Hot Water tank which got damaged was on the right side of duplex which despite the total destruction on left received no damage other than the tank which overheated when water pressure dropped in the street due to fire hydrants being opened during the fire sucking water out of the tank.
Because a foot and a half firewall from basement to roof made of Fire resistant brick was installed and maintained the unit on right had no damage at all.
This rarely happens usually units on either side receive significant water and smoke damage or actual fire damage but not in this case .
This just goes to show just how significant and important firewalls are in construction.
Another case where a firewall stopped significant damage was in a commercial strip mall in Cranberry Twp Pa. along US19 when a Play it again sport resale shop went up in flames and owner eventually convicted of arson.