check valves allow air and water to escape from the magazine into one of the ventilation ducts or through an independent air escape. Exhaust Vents Most magazines, particularly missile magazines, are  vented  to  the  atmosphere.  When  missile  motors burn, they rapidly produce large volumes of smoke and gas. If a missile motor should accidentally ignite in a magazine, the smoke and gas will be vented directly to the atmosphere, rather than to other areas of the ship. The  area  on  the  weather  deck  in  the  vicinity  of  an exhaust vent is potentially hazardous and is marked to warn personnel not to loiter in the area. Magazine Alarms Magazines are equipped with various alarm and sensing devices. When activated, they provide audible and visual warnings that something is wrong. An alarm may  mean  that  an  actual  problem  exists  or  that  a problem is developing. Designated personnel should investigate  any  activated  alarm  immediately.  The following paragraphs discuss three common alarms. FH ALARM CIRCUIT.—The FH alarm circuit is used with a magazine’s sprinkler system to indicate two system problems: leakage and activation. Leakage indicates  that  a  problem  is  developing.  Actuation means  that  water  is  flowing  and  the  ammunition  is getting sprayed. Actual sprinkling can result from a real fire or a high heat buildup in the magazine. It also can result from a gross sprinkler system malfunction. In  any  case,  appropriate  action  must  be  taken immediately. F  ALARM  CIRCUIT.—The  F  alarm  circuit  is also known as the high-temperature alarm circuit. It sounds  an  alarm  when  magazine  space  temperature reaches a dangerous level. If the F alarm sounds, you should investigate the problem immediately!   If you react  quickly  enough,  you  may  be  able  to  take measures to reduce the temperature. This may prevent the sprinkler system from activating. COMBUSTION GAS AND SMOKE DETECTOR.—Some  magazines  may  contain  a combustion gas and smoke detector. This detector is another  early  warning  device  similar  to  a  smoke detector  in  a  house.  It  detects  the  presence  of combustion gases and smoke particles in the air formed in all types of fires and in smoldering or overheated materials.  These  particles  are  so  small  that  they  are invisible to the human eye; however, they are present before there is any evidence of flame. MAGAZINE INSPECTIONS Aboard ship, magazine inspections are mandatory and  are  an  integral  part  of  the  ship’s  PMS.  These inspections must be conducted by qualified personnel using a check sheet (maintenance requirement card) to ensure  that  a  hazard  or  abnormal  condition  is  not overlooked. It is not within the scope of this manual to discuss in  detail  the  criteria  of  all  required  magazine inspections.  However,  we  can  provide  a  brief description   of   daily   magazine   inspection requirements. Daily Visual Inspections The daily visual inspection of magazines generally consists of checking for improperly secured stowage, unsatisfactory protective packaging, unusual fumes or odors, magazine cleanliness, and any other abnormal condition. Abnormal  conditions  in  a  ship’s  magazine  or ammunition  stowage  space  include  evidence  of tampering to gain access (broken, damaged, or missing locks),  evidence  of  theft,  and  the  presence  of unauthorized  materials.  Abnormal  conditions  also include  evidence  of  localized  overheating  from adjacent  compartments  on  decks,  bulkheads,  and overheads; indications of leaks from sprinkler or flood pipes, nozzles, or control valves and regulators; and inoperable or damaged reachrods, linkages, automatic fire alarm devices, and other similar equipment. Another  important  requirement  of  the  daily inspection is to observe, record, and report maximum and minimum temperature conditions. Magazine Temperatures Temperature  is  the  most  important  factor  that affects powder and propellant stability. This is why it’s important to monitor temperature conditions. Temperature readings are normally taken once a day. The exact time may vary, but most ships take the readings in the morning (around 0800 for example), using a special maximum and minimum thermometer (sometimes  called  a  high-low  thermometer).  Figure 5-5  illustrates  a  typical  maximum  and  minimum thermometer. 5-13