particularly true when the access to the compartment has been opened for the purpose of fighting the fire. The open
access in combination with an open ventilating duct will cause a natural draft. Ventilating system closures are provided
and fitted to assist in preventing the spread of smoke and fumes to other parts of the ship as well as for preservation of
watertight integrity and reserve buoyancy.
Section XV. PRECAUTIONS IN VENTILATING
6-25. PRECAUTIONS. When it has been definitely determined that the fire has been completely extinguished, natural
ventilation and forced ventilation, either by the installed systems or by portable ventilating fans, can be used very
advantageously for clearing compartments of smoke and fumes. However, prior to the introduction of ventilation, either
natural or mechanical, certain precautions must be observed:
a. Determine that the fire has been extinguished.
b. Investigate the ventilating systems to the affected area to make sure they are free from fire or smoldering
c. Have fire parties and equipment standing by the blower and controller of the ventilating system.
d. Have permission of the Engineering Officer to open the ventilating system closures and start the blower as
required to ventilate the compartment.
Exhaust systems should be used for clearing compartments of smoke fumes resulting from fires. The use of exhaust
systems will create an indraft from adjacent spaces and prevent the smoke and fumes from spreading. Supply systems,
if used, normally will force smoke and fumes into adjacent spaces causing possible smoke damage and further
inconvenience to personnel. Spaces directly open to weather can be cleared conveniently by use of supply systems.
Section XVI. USE OF PORTABLE VENTILATING BLOWERS
6-26. PORTABLE EQUIPMENT. Portable ventilating blowers are basically auxiliary equipment, and normally are not as
efficient or convenient as permanent ventilating systems. However, in the presence of explosive vapors or fumes, it may
be unsafe to use the permanent systems, and only portable ventilating blowers equipped with explosion-proof motors can
The axial-type blower is driven by an explosion-proof motor. It should be pointed out that while these motors are
explosion-proof when assembled by the factory, the explosion-proof quality is not necessarily present after overhaul; and
where there is a possibility of explosive vapors being present, the air turbine blower should be used in lieu of the electric-
driven blower with an overhauled motor.