The waterproof ventilator, shown in figure 17-6, consists of an outer housing, an inner ventilator shaft extending up to the other housing, and a bucket-type closure supported over the ventilator shaft by a compression spring. The bucket has drain tubes that extend into a sump between the ventilator shaft and the outer housing. The sump has scupper valves that drain onto the weather deck.

The ventilator operates automatically and is normally open. Small amounts of water, which enter the ventilator, fall into the bucket and drain out through the drain tubes and scuppers. In heavy seas, when water enters the bucket faster than it drains out, the weight of the water forces the bucket down against the top of the ventilator shaft. Thus, a watertight seal is formed and maintained until sufficient water drains out to permit the force of the spring to raise the bucket to the open position. Normally, some provision is made so that the ventilator can also be closed manually. With slight variations in construction, ventilation of this type may be used for both the supply and exhaust of air.

BRACKET FANS

Bracket fans are used in hot weather to provide local circulation. These fans are nor-mally installed in living, hospital, office, commissary, supply, and berthing spaces. Where air-conditioning systems are used, bracket fans are sometimes used to facilitate proper circulation and direction of cold air.

EXHAUSTS

Local exhausts are used to remove heat and odors. Machinery spaces, laundries, and galleys are but a few of the spaces aboard ship where local exhausts are used.

Most exhausts used on Navy ships are

mechanical (contain an exhaust fan), although natural exhausts are sometimes used in ships structures and on small craft.

Figure 17-6.-Waterproof ventilator (cutaway view).