atmosphere, and an oxygen analyzer is unreliable
COMPARTMENT REMANNING
when its sensor is exposed to excess moisture or comes
Once the space is certified safe, remanning can
in contact with particulates found in a post-fire
atmosphere.
begin. A careful damage assessment is conducted, and
once individual equipment or systems are verified
When the space is clear of smoke, test the
operational and safe, then may be placed in service.
atmosphere for oxygen, combustible gases, and toxic
gases. The level of oxygen must be between 19.5 and
INVESTIGATION
22 percent. Combustible gases must be less than
10 percent of the lower explosive limit, and all toxic
After overhaul, the fire should be investigated to
gases must be below their threshold limits before the
determine the point of origin, types of combustibles
space is certified safe for personnel without breathing
involved, path of fire spread, ignition source, and
devices. After a class BRAVO fire, the compartment
s i g n i fi c a n t eve n t s i n t h e g r ow t h a n d eve n t u a l
should be tested for the following gases:
extinguishment of the fire. Starting from the point of
Hydrocarbons
farthest fire spread, burn patterns will usually extend
back to the area of origin. Efforts should be directed
Carbon dioxide
toward recreating the conditions that caused the fire,
Carbon monoxide
and identifying any changes in design or procedures
that could have prevented the fire or lessened its
spread and intensity. These changes are very helpful
to ship designers and operators. Photographs,
Hydrogen cyanide
material samples, metallurgical samples, and failed
equipment assist in reconstructing a fire history. If
If Halon 1301 was discharged into the
compartment, a test for hydrogen fluoride must also be
there is a major fire which involves significant
conducted. Shipboard personnel authorized to conduct
damage or loss of life, a NAVSEA technical expertise
these tests aboard ship are the gas free engineer and gas
team is available to investigate such fires, and to
free petty officers. Required tests shall be conducted
develop lessons learned from a ship design and a
near the center and at all four corners, on each level of
material standpoint.
the compartment. At least one satisfactory reading at
each location must be obtained.
REVIEW QUESTIONS
Specific information regarding testing procedures
and equipment is found in Naval Ships' Technical
Q17.
What percentage(s) of oxygen must be
Manual (NSTM), chapter 074,volume 3, "Gas Free
Engineering." If the compartment has been exposed to
present when conducting post-fire
a CBR environment, decontamination procedures
atmospheric testing of a compartment?
detailed in NSTM, chapter 470, "Shipboard BW/CW
1.
Less than 10 percent
2.
19.5 to 22
percent
DEWATERING
3.
30
to 33
percent
Dewater the compartment with the commanding
4.
40
to 42.5 percent
officer's permission, and in accordance with operating
Q18.
Halon 1301 was discharged into the
procedures. Dewatering a class BRAVO pool fire will
compartment to extinguish a fire. This
not commence until the space is completely
requires a test be conducted for which of the
overhauled, except in extreme conditions where ship
stability is threatened. Dewatering will affect the vapor
following types of gas?
barrier on top of pooled flammable liquid, an extreme
1.
Hydrogen sulfide
caution must be exercised to ensure the AFFF blanket
is maintained until completion of overhaul. Following
2.
Carbon monoxide
overhaul, normal dewatering may be conducted or
3.
Hydrogen flouride
completed at the same time as desmoking or post-fire
4.
Hydrogen bromide
gas free testing.
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