achieve compartmentalisation, a passive fire protection measure; see firewall (construction). On an aircraft, bulkheads divide the cabin into multiple areas. On passenger aircraft a common application is for physically dividing cabins used for different classes of service (e.g. economy and business.) On combination cargo/ passenger, or "combi" aircraft, bulkhead walls are inserted to divide areas intended for passenger seating and cargo storage. Requirements of bulkheads Fire-resistance Openings in fire-resistance rated bulkheads and decks must be firestopped to restore the fire-resistance ratings that would otherwise be compromised, if the openings were left unsealed. The authority having jurisdiction for such measures varies depending upon the flag of the ship. Merchant vessels are typically subject to the regulations and inspections of the Coast Guards of the flag country. Combat ships are subject to the regulations set out by the navy of the country that owns the ship. Prevention of damage from EMI and EMP Bulkheads and decks of warships may be fully grounded (electrically) as a countermeasure against damage from EMI and EMP due to nuclear or electromagnetic bomb detonations near the ship, which could severely damage the vital electronic systems on a ship. In the case of firestops, cable jacketing is usually removed within the seal and firestop rubber modules are internally fitted with copper shields, which contact the cables' armour in order to ground the seal. Automotive Most passenger vehicles and some freight vehicles will have a bulkhead which separates the engine compartment from the passenger compartment or cab; the automotive use is analogous to the nautical term in that the bulkhead is an internal wall which separates different parts of the vehicle. Some passenger vehicles (particularly sedan/saloon-type vehicles) will also have a rear bulkhead, which separates the passenger compartment from the trunk/boot. Other uses of the term The term was later applied to other vehicles, such as railroad cars, hopper cars, trams, automobiles, aircraft or spacecraft, as well as to containers, intermediate bulk containers and fuel tanks. In some of these cases bulkheads are airtight to prevent air leakage or the spread of a fire. The term may also be used for the "end walls" of bulkhead flatcars. Mechanically, a partition or panel through which connectors pass, or a connector designed to pass through a partition. In architecture the term is frequently used to denote any boxed in beam or other downstand from a ceiling and by extension even the