Carbon Dioxide (CO2)
enough for the fire to be extinguished. Several types of
dry chemicals have been used as fire extinguishing
Halon 1301
agents. For Navy use, the most important agent of this
The agent or agents that are used in any particular
kind at present is potassium bicarbonate, also known as
case will depend upon the classification of the fire and
Purple-K-Powder (PKP). PKP is used to extinguish
the general circumstances.
class B and class C fires because it is very effective
against these fires. However, it is both corrosive and
WATER
abrasive and should be used on class C fires only in
emergencies. PKP is available in 18-pound and
Water is a cooling agent, and onboard ship the sea
27-pound portable extinguishers. PKP can be used in
provides an inexhaustible supply. If the surface
conjunction with AFFF. Portable PKP extinguishers
temperature of a fire can be lowered below the ignition
and the special equipment for using PKP and AFFF
temperature of the fuel, the fire will be extinguished.
together are described in chapter 5 of this NRTC.
Water is most efficient when it absorbs enough heat to
raise its temperature to 212F (100C). At this
CARBON DIOXIDE
temperature, the seawater will absorb still more heat
until it changes to steam. The steam carries away the
Carbon dioxide (CO2) is an effective agent for
heat and results in the lowering of the temperature of
extinguishing fires by smothering them; that is, CO2
the surface.
r e d u c e s t h e a m o u n t o f o x y g e n ava i l a b l e f o r
combustion. This smothering action is temporary and
AQUEOUS FILM-FORMING FOAM (AFFF)
you must remember that the fire can quickly rekindle if
oxygen is again admitted to the hot embers.
Foam is a highly effective extinguishing agent for
smothering large fires, particularly those in oil,
CO2 is a dry, noncorrosive gas that is inert when in
gasoline, and jet fuels. AFFF, also known as "light
contact with most substances. It is heavier than air and
water," is a synthetic, film-forming foam designed for
remains close to the surface. CO2 does not damage
use in shipboard fire-fighting systems. The foam
machinery or other equipment. Since it is a
proportioning/injection equipment generates a white
foam blanket. AFFF proportioning equipment is
fight fires that might present electric shock hazards.
discussed in chapter 6 of this nonresident training
However, the frost that collects on the horn of a CO2
course (NRTC).
extinguisher does conduct electricity. Therefore, you
AFFF is equivalent to seawater when it is used to
should be careful and never allow the horn to come into
extinguish class A fires. The unique action of AFFF
contact with electrical components. Aboard ship, CO2
stems from its ability to make a light water film float on
fire extinguishing equipment includes 15-pound CO2
flammable fuels. As foam is applied over the
extinguishers, 50-pound CO2 hose and reel
flammable liquid surface, an aqueous solution drains
from the foam bubbles and floats out over the surface to
systems. Although CO2 is nonpoisonous, it is
provide a vapor seal. This aqueous film-forming action
dangerous because it does not provide a suitable
enhances extinguishment and prevents reflash, even
atmosphere for breathing. Asphyxiation can result
when the foam blanket is disturbed. Fuels which have
from breathing CO2; therefore, an oxygen breathing
not been ignited may also be protected with this same
apparatus (OBA) must be worn when CO2 is used
action. AFFF can be used alone or in combination with
below decks or in confined spaces.
Purple-K-Powder (PKP).
HALON 1301
PURPLE-K-POWDER (PKP)
Halon 1301 is a colorless, odorless gas with a
Dry chemical powders extinguish a fire by a rather
density approximately five times that of air. It does not
complicated chemical mechanism. They do not
conduct electricity or leave a residue. Halon 1301 is
smother the fire and they do not cool it. Instead, they
stored in compressed gas cylinders for shipboard use.
i n t e r r u p t t h e c h e m i c a l r e a c t i o n o f t h e fi r e b y
This extinguishing agent is effective against class A,
suspending fine particles in the fire. In effect, the dry
class B, and class C fires. The fires are not extinguished
chemicals put a temporary screen between the heat,
by smothering or cooling; instead, the chemical
oxygen, and fuel and maintain this screen just long
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