Portable axial fans (fig. 10-17 view B) with flexible air hoses are used aboard ship for ventilating holds and cofferdams. They are also used in unventilated spaces to clear out stale air or gases before personnel enter and for emergency cooling of machinery.

Figure 10-16.-Vane-axial fan: A. Exterior view. B. Cutaway view. C. Cutaway view of the fan motor.

Most portable fans are of the axial-flow type, driven by electric, explosionproof motors. On ships carrying gasoline, a few air turbine-driven centrifugal fans are normally provided. You can place greater confidence in the explosionproof characteristics of these fans.

CAUTION

Never use a dc-driven fan to exhaust air that contains explosive vapor.

EXHAUSTS

Many local exhausts are used to remove heat and odors. Machinery spaces, laundries, and galleys are some of the shipboard spaces where local exhausts are used.

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

Figure 10-17.-Miscellaneous ventilation fans: A. Centrifugal fan. B. Portable axial fan.