motors burn, they rapidly produce large volumes of smoke and gas. To avoid spreading smoke and gas to other areas of the ship if a missile motor in a magazine accidentally ignites, the exhaust ducts are vented to the atmosphere. The area on the weather deck in the vicinity of an exhaust vent is potentially hazardous, and it is marked to warn personnel not to loiter (hang around) in this area. SPRINKLER AND ALARM SYSTEMS Primary and missile magazines, ammunition handling rooms and most ready-service magazines are fitted with sprinkler systems. Sprinkler systems consist of  spray  heads  or  sprinkler-head  valves  arranged  to dash  water  directly  on  the  munitions  and  completely cover  the  magazine's  interior.  Sprinkler  systems  for spaces located below the damage control deck (second deck on aircraft carriers) are arranged for local control at  the  valve  and  for  remote  control  from  the  damage control  deck.  On  aircraft  carriers,  the  remote  controls are    normally    divided    into    two    groups—forward sprinkler control board and aft sprinkler control board. The  forward  magazine  group  and  the  aft  magazine group sprinklers can be remotely activated from the two control boards. Sprinkler systems for spaces located on and  above  the  damage  control  deck  are  arranged  for local  control  only  from  a  position  outside  the  access entrance to the space. NOTE: Some magazines are designed without sprinkler systems so water-activated ammunition   can   be   stowed   in   them.   For example,   Mk   58   marine   location   markers cannot  be  stowed  in  magazines  that  can  be flooded. Also, weather-deck lockers and 20-mm and 40-mm ready-service rooms do not require sprinkler systems. Sprinkler Systems Sprinkler  systems  are  classified  by  the  type  or location  of  the  control  exercised  over  the  valves  that restrain   the   flow   of   water.   These   valves   may   be operated  manually  or  by  remote  control  (manually  or automatically).    There    are    three    types    of    remote operation: 1. Manual, by operating gears 2. Hydraulic,   by   means   of   control   cocks   and water from the fire system or control cocks and oil pressure supplied by hand pumps 3. Automatic,   by   means   of   a   rate of rise   or combined  rate of rise  and  fixed  temperature thermopneumatic control system The  rate of rise  is  indicated  in  a  magazine  when  the temperature increases rapidly (such as from a fire). The rapid temperature increase activates the sprinkler-alarm device   (FH   circuit),   which,   in   turn,   automatically activates the sprinkler system control valve. Alarm Systems There    are    three    alarms    that    are    commonly associated   with   all   magazine   sprinkler   systems—a sprinkling  (FH  circuit)  alarm,  a  flooding  (FD  circuit) alarm, and a high-temperature (F circuit) alarm.   High-temperature alarm systems (F circuit) are installed  in  all  of  the  following  magazines  or spaces:   Ammunition and propellant stowage areas   Ammunition handling spaces   Ammunition   assembly/disassembly/check-out areas   Cargo ammunition holds to provide a means of determining high temperatures Don't confuse the F circuit with the FH circuit. The F circuit detects a slow rise in temperature while the FH circuit detects a rapid rise in temperature. Install   a   minimum   of   two   thermostats   in   each space.  Install  a  minimum  of  one  thermostat  for  each 250 square feet of deck area, or fraction of a deck area. If   high   temperatures   occur   in   any   of   the   spaces containing    thermostats,    the    high-temperature    that occurrence   is   indicated   on   an   alarm   switchboard installed in an area continuously manned when the ship is  underway.  Usually,  this  is  damage  control  central. Audible   alarm   systems   are   also   installed   in   the pilothouse, officer-of-the-deck (OOD) area, secondary damage control station, and each interior communications   room.   The   audible   alarm   systems work in conjunction with the F and FH circuits. Tests  and  maintenance  of  the  magazine  sprinkler systems    are    performed    periodically    according    to NAVSEA    and    applicable    preventive    maintenance system (PMS) instructions. MAGAZINE INTERNAL ARRANGEMENT The  internal  arrangement  of  each  magazine  may vary  considerably.  The  arrangement  depends  on  the 11-12