H2S

1. CNPC Niger Petroleum S.A.
CNPC Global Solutions Co. Ltd.
CNPC Niger Petroleum S.A.
General HSE Training
Lecture 4: Hydrogen Sulfide Awareness

2. Contents
Lecture 4: Hydrogen Sulfide Awareness
1. Introduction
2. What is Hydrogen Sulphide?
3. Hazards OF Hydrogen Sulfide
4. H2S Area Classification
5. Procedures and control
6. Personal Protective Equipment/Respiratory protection

3. Introduction
Objectives
• Recognize the properties of Hydrogen Sulfide and associated
Hazard
• Be able to demonstrate your ability to successfully protect yourself
within H2S contaminated areas
• Recognize different roles and responsibilities within H2S working
at sour crude facilities.
• To be aware of the hazardous nature of H2S
• To be able to minimize the risks to people from Hydrogen is as
low as reasonably practicable
• To be familiar with the emergency procedure in the event of H2S
release

4. What is Hydrogen Sulphide
What is Hydrogen Sulphide?
• Hydrogen Sulphide like air is a colorless gas
• It is highly Toxic – it kills quickly at high
concentrates
• It is extremely flammable
• It can be explosive
• H2S smells like rotten eggs at low concentration.
• With continued exposure, your ability to smell will
become paralyzed It is highly corrosive to certain
metals – especially copper

5. What is Hydrogen Sulphide
H2S:
• Invisible
• Flammable
• Explosive
• High Toxic
• Corrosive

6. What is Hydrogen Sulphide
Where would we find H2S in oil and gas
field?
• Naturally in crude oil and gas (different
reservoirs – different levels)
• In the well-bore during drilling
• In pipes and vessels during maintenance
“break-ins”
• Accidental release
• From the decomposition of organic materials
(sewage)
• In stagnant marsh-water (reduced oxygen).

7. Hazards OF Hydrogen Sulfide
Hazards OF Hydrogen Sulfide
Odorless
• H2S is heavier than air, so it collects
in low-lying areas.
• The odor may be masked or hidden
by other strong chemical smells –
such as hydrocarbons.

8. Hazards OF Hydrogen Sulfide
• H2S is extremely flammable (4, NFPA).
• If there is enough Hydrogen Sulphide in the air
between 43,000 and 460,000 ppm (Flammability
range: 4.3% - 46%) and the temperature is right, it
will explode.
• When burning, H2S emits another dangerous
chemical - Sulphur Dioxide ( SO2 ) .
• SO2 severely irritates eyes, nose, throat and
respiratory system.

9. Hazards OF Hydrogen Sulfide
What is ppm?
• PPM is an abbreviation meaning – Parts Per Million
• In other words - A measure of small volumes that are a part of larger
ones:
• 1 percent = 10,000 ppm (1/100 x 1,000,000)
or
• 1 ppm = 0.0001 percent
• Approximately 1 glass of water in a swimming pool is roughly
equivalent to 1ppm

10. Effects from Exposure
Concen. (ppm) Effects Observed
0.0025 -10 Easily detected, moderate odour
5 Long Term Exposure Limit: 8-Hour TWA value
10
Unpleasant odour. Possible eye irritation.
Short Term Exposure Limit: fixed at 10 ppm (15mg/m³) the 15 minute TWA value
30 Low concentration: possible respiratory effects and eye irritation
50-100
Loss of sense of smell after about 15 minutes exposure.
Irritation of throat and eyes. Altered respiration, pain in the eyes and drowsiness after 15-30 minutes followed by
throat irritation after 1 hour.
100-200
Loss of sense of smell within seconds, with irritation of throat and eyes.
Haemorrhage and death beyond 8 hours exposure.
200-500
Loss of balance and consciousness within 30 minutes and paralysis of the respiratory system. Artificial respiration
must be applied immediately.
Haemorrhage and death after 2 to 4 hours exposure.
500-700
Loss of consciousness within 15 minutes of exposure.
Respiration stops and death may result after 15 to 30 minutes exposure if the victim is not immediately treated.
700-1,000
Immediate loss of consciousness.
Brain damage or death if first aid is not immediately applied. Death after 15 minutes exposure.
1,000-1,500 Immediate collapse and death after 2 minutes exposure.
Above 1,500 Immediate death
Hazards OF Hydrogen Sulfide

11. Hazards OF Hydrogen Sulfide
Exposure Limits
• WEL – Workplace (Shift) Exposure Limit.
 The WEL for Hydrogen Sulphide is 5 ppm.
 This is an amount you can safely breathe, based on an eight hour
day over a five-day work week.
• STEL – Short Term Exposure Limit.
 The STEL for Hydrogen Sulphide is 10 ppm.
 This is now much you can safely be exposed to averaged over a
15 minute period.
 The STEL should be checked four times a day, when your risk is
likely to be the greatest.
 Over 10 ppm – a respirator is required – even for short duration.

12. Hazards OF Hydrogen Sulfide
Hydrogen Sulphide
• Remember, these are just guidelines.
• Reactions to H2S are different from
person to person and depend, mostly on
its concentration and the duration of
exposure.

13. Hazards OF Hydrogen Sulfide
Hydrogen Sulphide
• H2S is soluble in water, Oils, and most organic liquids.
• When agitated or when temperatures increases, solubility
decreases and higher concentrations Of H2S are decreased.
• Also, acidic solutions Containing H2S can severely irritate your
skin and eyes.

14. Hazards OF Hydrogen Sulfide
Hydrogen Sulphide
• Hydrogen Sulphide reacts violently to strong oxidizers, metal
oxides, peroxides, strong alkalis, active metals and some plastics
and rubbers.
• It is corrosive, forming the spontaneously ignitable by-product “
Iron Sulphide scale.”
• This by-product is often found in vessels and pipes containing H2S.
• When cleaning such equipment, keep all surfaces wet to avoid
ignition.

15. Hazards OF Hydrogen Sulfide
Immediate Danger Level
• IDLH – Immediate Danger to Life or Health 100 ppm.
• Based on 15 minute escape level.
• SCBA Only where limits potentially exceed this level.

16. H2S Area Classification
Area Classification
• Category 0: H2S is known to be present during normal operations,
e.g. in vessels and confined spaces.
• Category 1: H2S may be present during normal operations, e.g.
mud tanks and shale shaker areas.
• Category 2: Area is normally free of H2S, but breach of
containment or leaks may create risk:
• Category 2A: Less than 500 ppm H2S in the process stream.
• Category 2B: More than 500 ppm H2S in the process stream.

17. Zone Controls
H2S Area Classification

18. Procedures and control
Procedures and control
• Planning:
 Label and colour-code plant and equipment that may contain
H2S.
 Classify areas and decide the use of fixed/portable H2S
detectors.
 Prepare a contingency plan that covers H2S emergencies.
 Mark up site plans with H2S and safe areas.

19. Procedures and control
Control:
 Remove H2S through chemical treatment methods, e.g. H2S
scavengers, use of biocides to prevent growth of sulphate reducing
bacteria.
 Isolate and depressurize enclosed systems before breaking
containment.
 Purge residues and ventilate to remove H2S.
 Provide forced ventilation, e.g. on air blower where there is no
through draught.
 Respiratory protective equipment is normally required
 Ensure thorough gas-testing is carried out – using calibrated
equipment - for H2S.

20. Procedures and control
Access:
 Restrict access to areas where H2S is known or suspected.
 Post H2S warning notices at points of access to Category 0 and
Category 1 areas.
 Fit air direction and air movement indicators or windsocks in areas
that rely on natural ventilation for H2S control.

21. Procedures and control
Air Monitoring
 Fixed Monitor located where wide spread H2S contamination is
possible.
 Alarms that can be seen and heard when H2S levels exceed the PEL
(Permissible Exposure Limit) and STEL.
 Portable Monitors that you either hold in your hand or attach to
yourself.
 Transportable gas detectors.

22. Procedures and control
Engineering Controls
 The most widely engineering control is ventilation :
 Natural ventilation: It comes from airflow.
 If you are relying on natural ventilation, remain alert for the safest
way to escape by noting which way wind socks, streamers and
flags are blowing.
 This is called being “wind conscious”.

23. Procedures and control
Mechanical Ventilation:
 It is common in confined space
where only fans and blowers can
move the air.

24. Personal Protective Equipment/Respiratory
Personal Protective Equipment/Respiratory (PPE/ RPE)
• Personal protective equipment (PPE)
• Ensure that all items of PPE are compatible.
• RPE will be required for work in all areas where H2S concentrations
exceed the WEL.
• Respiratory protective equipment (RPE)
• Provide CE-marked (or equivalent) positive pressure BA with an
assigned protection factor (PF; is the level of protection expected by
either a certain class of respirators or by the wearer) of at least 40.

25. Personal Protective Equipment/Respiratory
Respiratory Protective Equipment
• Escape Units:
 Are completely self-contained.
 Equipped with an air cylinder rated for five minutes.
 Used only to escape from (not enter) a hazardous
area.
• Air Lines units:
• Have an air line or hose that supplies air during
normal use.
• Equipped with a self-contained emergency-escape
air cylinder in case the air-line supply fails.

26. Personal Protective Equipment/Respiratory
Respiratory Protective Equipment
• SCBAs:
• Have an air cylinder rated for 15 or more
minutes.
• Used to enter a hazardous environment.
• The most flexible because they allow you to
move from area to area, even if you have to
disconnect from the air-line supply.
• Equipped with devices that warn you when
approximately five minutes of air remain.

27. Personal Protective Equipment/Respiratory
Maintenance, Examination and Testing of RPE
• Checking and maintenance:
 Before use, check the air lines for supplied-air BA.
 Before each use, check that portable/personal gas monitors are
fully charged and working properly.
 Follow the planned maintenance regime (PMR)
 Ensure that fixed H2S detectors and alarms are working properly
and fail to the ‘alarm’ state.
 Keep this information in the testing logbook.

28. Personal Protective Equipment/Respiratory
Examination and testing:
• Examine and test RPE thoroughly at least monthly and for
infrequently used RPE at least three monthly.
• Replace worn parts.
• Check the airflow and air quality to air-fed RPE at least once every
three months, or before use.
• Check in-line filters.
• Ensure that breathable air compressors take in clean air.
• Keep records of tests for 5 years.

29. Personal Protective Equipment/Respiratory
Avoiding Exposure
• To avoid exposure to H2S
• Know where to find:
 Emergency Exits
 Safe assembly areas
 Emergency SCBA.

30. Personal Protective Equipment/Respiratory
To avoid exposure to H2S :
• Remain “wind conscious”
• Pay attention to wind socks, streamers and flags
• Make sure enough fans and blowers are being used
• Know how to use air-monitoring devices
• Don’t smoke.
• Remember, hydrogen Sulphide is highly explosive and flammable.
• Be aware of safety rules, warning signs and your company’s H2S
procedures.

31. Personal Protective Equipment/Respiratory
• Hydrogen Sulphide is deadly, especially when you don’t understand and
respect its dangers.
• Take Hydrogen Sulphide seriously .
• It’s a matter of life or death.

32. A Better You, A Better Niger
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