593-Dangers of Hydrogen Sulphide (H2S) / 748
D
an
g
ers of
Hy
dro
g
en Sul
ph
ide
BOS-PRD-03.900907
Version 04. Original date: 25/05/2012. Version date: 31/12/2014. Valid version only on QMS site. Uncontrolled document when printed.
Procedure prepared by: BOS QHSE Coordinator. Approved by: BOS QHSES Manager. Validated by: BOS Quality Representative
5 / 7
4
D
escri
p
tion
4
.1
D
an
g
ers of
H
2
S
x
H
2
S is an extremely toxic gas that naturally occurs in some sub-sea offshore drilling and exploration
activities;
x
H
2
S may also be present in unventilated spaces which have contained ballast water which has
become stagnant due to the rotting of organic material in the water;
x
H
2
S has the highest level of toxicity of all naturally occurring gases and even in small amounts, has a
strong sulphur smell that is comparable to that
of “rotten eggs”;
x
H
2
S is heavier than air and therefore will become more concentrated in nearer the deck or ground;
x
H
2
S is also explosive when combined with air at a range between 4.3 to 45.5 percent by volume.
4
.
2
Th
e identification of
H
2
S
x
Close liaison
shall
be conducted between the vessel
Master
and the
Offs
h
ore
I
nstallation
Mana
g
er
(
O
I
M
)
to ensure that any potential areas that may be expected to produce H
2
S are fully
communicated;
x
The smell of “rotten eggs” is the initial factor which identifies the presence of
H
2
S. When this occurs
the
Master
,
Base Mana
g
er
and
C
ontracts Mana
g
er
shall
be informed. At this stage the
concentration will be below 10ppm;
x
Should the smell of “rotten eggs” subsequently disappear this
shall
not be interpreted that the H
2
S
concentration has decreased. As the concentrations increases, so the ability to smell it decreases.
Any signs of dizziness or coughing
should
be immediately interpreted as a rising concentration.
Death can quickly follow should the concentration continue to rise above 50ppm.
4
.
3
Th
e effects of
H
2
S
C
oncentration
Effect
0
–
10 ppm
Smell of “rotten eggs”
Irritation of the eyes, nose and throat
10
–
50 ppm
Smell of “rotten eggs” decreases
Headache
Dizziness
Nausea and vomiting
Coughing and breathing difficulty
More than 50 ppm
Smell of “rotten eggs” disappears
Shock
Convulsion
Coma
Death
4
.
4
G
eneral
p
recautions to
b
e ta
k
en
Whenever operating in any known or suspected H
2
S areas:
x
Pre-task planning is vitally important to ensure that awareness is maintained and that all personnel
are prepared to take emergency action should this be required;
x
The
Master
shall
ensure that each person who may be affected is informed of the potential hazards
associated with H
2
S and the precautions that
shall
be adhered to;
593