Magazines are fitted with appropriate environmental control and safety features to protect their ammunition from excessive temperatures and humidity.

Most magazines are equipped with mechanical cooling or ventilation systems. However, there are a few magazines that do not have either of these features. If a magazine without controls shows a heat gain in excess of 100 F, portable ventilation systems are used to prevent overheating or condensation of moisture.

Supply and Exhaust Ventilation

Ventilation ducts and exhaust ventilation outlets to and from magazines provide forced-air ventilation. Air is forced through the ducts by electric fans installed within the ducting. Standard covers maintain water-tightness keep flames caused by hits on the ship during combat from entering the magazines. These covers must always be closed during combat (general quarters) conditions unless there are imperative reasons for doing otherwise.

Certain types of ammunition may produce fumes that, if inhaled, may have a slightly intoxicating effect. However, this should not appreciably reduce individuals' work efficiency. Generally, there is sufficient air volume in large sealed magazines and handling rooms to provide a safe working atmosphere.

Frequently, in hot climates, magazines can be maintained at a lower average temperature by closing off the supply of air during the heat of the day and running the blowers only at night when cool air can be forced in. During the day the magazine will heat slowly by conduction rather than rapidly by the introduction of heated air.

Magazine Vent Check Valves

It may be necessary to operate the sprinkler system in magazines while the ventilation valves are secured. During these times; the magazine must be vented by an air escape to ensure that the pressure within the magazine will not build up beyond the allowed pressure limits of the watertight boundaries. Magazine 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.