In the physical world, a firewall is a
wall built to prevent the spread of a fire from building to building or from one section of a building to another. To this end, a firewall is constructed of much sturdier material than the other walls, and is generally
windowless and
doorless and otherwise devoid of any openings through which a fire could spread. For the same reason, firewalls also typically extend all the way from ground to
roof level or beyond. Firewalls are rated in terms of hours they can withstand a fire, e.g. one-hour firewall, two-hour firewall, three-hour firewall, etc., depending on the material and construction method of the wall.
The term "firewall" is also used to describe a thick metal plate, in vehicles such as automobiles and aircraft, which separates the fuel tank from the rest of the engine and/or the interior of the vehicle to prevent explosions and protect passengers from serious injury or death in the case of a fuel leak or engine fire.