FIRE EXTrtfGUISHEKS 173
have been adopted by the International Convention for the Safety of
Life at Sea, and are to take effect when ratified.
3. Describe how steam is injected into a hold in the event of fire.
Forcing steam into the hold will keep doWn combustion if it does not
actually put out the fire. The ends of suitable pipes are coupled to
the winch steam pipes on deck, the other ends being inserted into the
hold either by way of the ventilators, or the hold sounding pipes which
should have holes perforated in their lower ends, or through holes cut
in the hatches or deck as near to the seat of the fire as possible. All
hatches and openings into the compartment must be covered to prevent
any oxygenised air getting in. The pressure and the volume of steam
admitted into the hold should be capable of forcing its way into the air
spaces and escaping through any crevices or leakages in the walls of
the compartment, thus preventing the admission of air. The tempera-
ture of the hold will, of course, rise as evidenced by the heating of decks
and bulkheads, but the object is to keep the fire from bursting into flame,
and cases are on record where this method has kept the fire smouldering
slowly for days and weeks until the ship arrived in port and only on
opening the hatches has the fire become active. In some cases the fire
has been put out, the charred remains of packages in the hold testifying
to the effectiveness of steam in absorbing the oxygen in the hold.
4. Describe some types of fire extinguishers.
Portable Chemical Fire Extinguishers are universally known. They
are manufactured to approved specifications and have a capacity up to
3 gallons as that is the largest size that can be handled usefully by one
man. The liquid in the cylinder is contained under pressure, about
200 Ifos. per square inch, and squirts out when the valve is opened. The
charge may be (1) a solution of sodium bicarbonate or potassium carbon-
ate and a jar or bottle containing either sulphuric or hydrochloric acid;
(2) a capsule of compressed carbon dioxide, C02, of sufficient quantity
to make the fresh water in the cylinder an effective chemical extinguisher
and to exert sufficient pressure to be able to eject the whole fluid a
distance of 20 to 30 feet for a period of not less than 60 seconds.
"Firefoam" is another extinguishing medium which is specially
effective in the case of oil fire originating in engine and boiler spaces or in
tanks. Oil, in quantity, burns on the surface of water so that a solid jet
of water from a nozzle when turned on t«* the flames merely causey