1. ST-7.24 H2S Safety

2. ST-7.24 H2S Safety
REV
DATED
APPROVAL 01
VP (HSEQ)

3. “No hazards down here mate!
P.A.W.S for thought
“No hazards down here mate!

4. How is Hydrogen Sulphide formed
H2S is a by-product formed when organic matter decays
It is generated as a common by-product of industrial and manufacturing processes
Hydrogen Sulphide is formed under low oxygen conditions when sufficient amounts of Sulphur and bacteria are present, e.g.
Oil and gas reservoirs
Sewers and sewage processing facilities
Dark damp places where bacteria is present

5. Key Hazard Data Description Fire and Explosion Hazard:
Colourless gas: Offensive strong odour similar to rotten eggs.
Fire and Explosion Hazard:
Flammable gas, forms explosive mixtures with air.
Flammable Range:
LEL: 4.3% / UEL: 45%.
PEL
20 PPM.
IDLH
100 PPM
Vapour Density:
1.2, (vapours are heavier than air)
Chemical Abstract Service (CAS) Number

6. Concentration Levels & Effects
Health Effects
10 ppm
Beginning eye irritation
ppm
Slight respiratory tract irritation after 1 hour exposure.
100 ppm
Coughing, eye irritation, loss of sense of smell after 2-15 minutes. Altered respiration, pain in the eyes, and drowsiness after minutes followed by throat irritation after 1 hour. Several hours exposure results in gradual increase in severity of these symptoms and death may occur within the next 48 hours
ppm
Severe respiratory tract irritation after 1 hour of exposure. Possible pulmonary edema (fluid in the lungs).
ppm
Loss of consciousness and possibly death in 30 minutes to 1 hour.
700-1,000 ppm
Rapid unconsciousness, loss of respiration, and death after 1-3 minutes.
1,000-2,000ppm
Unconsciousness at once, loss of respiration and death in a few minutes. Death may occur even if individual is removed to fresh air at once.

7. Hazardous Characteristics
Toxic
H2S is the second most toxic gas known to man.
The most toxic is Hydrogen Cyanide
PEL of H2S = 10 ppm
PEL of HCN = 10 ppm

8. H2S as an Asphyxiant Asphyxiants Chemical Asphyxiants interfere with
Interfere with body’s ability to use oxygen
Chemical Asphyxiants interfere with
Oxygen transportation via hemoglobin or
Oxygen utilization by mitochondrial
cytochrome oxidase (cyt a,a3)

9. Asphyxiants Typical Toxicants Predominant Route of Exposure
Predominant Targets of Toxicity
Predominant Toxicodynamics
Simple Asphyxiant
Carbon dioxide
Propane
Butane
Inhalation
Cardiovascular
Disability
Displacement of oxygen from ambient atmosphere
Chemical Asphyxiant
Isobutyl nitrite
Carbon monoxide
Hydrogen cyanide
Hydrogen Sulphide
Hydrogen azide
Interfere with oxygen transportation in blood or oxygen utilization in other tissues
How will these patients present?

10. Toxic Hazard, Question
If the flare stack is burning away 100,000ppm H2S and is burning at 80% efficiency, what is the ppm of H2S in the exhaust plume?
100,000ppm. The flare stack is burning 80% of the volume not the concentration.

11. Hazardous Characteristics
When H2S is burned, it produces
Sulphur Dioxide “SO2”
Short-term exposures to high levels of Sulphur Dioxide can be life-threatening.
Exposure to 100 ppm of Sulphur Dioxide is considered immediately dangerous to life and health (IDLH)
PEL for SO2 is 2 ppm
Sulphur Dioxide may cause heart problems and respiratory disorders in younger children and elders.

12. Hazardous Characteristics
Iron Sulphide
H2S reacts with iron and steel which forms iron sulphide which can be Pyrophoric !

13. Hazardous Characteristics
Metallurgy
H2S may react with iron and steel causing hydrogen embrittlement and/or sulfide stress cracking. This lowers safety factors in tubular
and pressure vessels.

14. Hazardous Characteristics
Corrosive
H2S dissolves in water to form a weak acid that corrodes and pits metals.

15. How do we control this toxic gas?
Engineering Controls
Ventilation
Natural
Manufactured
Flare Stack
Venting
PPE
Supplied Air Respirator
SCBA
Work line
Escape Pack

16. Preventing Exposure
Personnel who are working on sites or in locations that may have H2S present should be provided with appropriate PPE including a personal H2S monitor.
Any site that has the potential for H2S shall be noted and workers informed of the potential hazards.
Look for signs or other indicators that demonstrate the potential for H2S at the site.
Ensure that you have a properly functioning H2S monitor prior to entering a site with the potential for H2S exposure.
Supplied Air Respiratory (SAR) escape may be required in some situation and this is to be addressed in the Site Specific Plan and/or Risk Assessment

17. Atmospheric Monitoring
Atmospheric monitoring should be done whenever there us potential for concentrations of H2S to be released
This includes
Confined space entry
When potential for exposure exists
Monitoring needs to be undertaken for
Toxicity
Flammability
Oxygen

18. Hydrogen Sulphide (H2S) Detection
Zero Maintenance
Sensor Range ppm
Low Alarm 10 ppm
High Alarm 15 ppm
-40 to +50 C

19. Multigas detector

20. Colourmetric indicator tubes
There are 11 different H2S detector tubes available for H2S.
Recommended Tube is:
Drager Hydrogen Sulphide 2/b Tubes Range: ppm Drager Detector Tubes

21. PID and H2S IE =10.45 EV 10.6 EV Bulb CF = 3.3 11.7 EV Bulb CF = 1.5
WARNING
NRC use 10.6 EV Bulb units calibrated on Isobutylene so any reading must be multiplied by 3.3 to get the actual reading. PID will not detect Sulphur Dioxide
PID is an excellent tool for gross readings but generally poor for specific substances unless in isolation.
The PID measures Volatile Organic Compounds (VOC’s)
A PID is easy to use but takes an experienced user to get the best out of it. Use incorrectly it can add to the hazard.
Remember that it will not detect everything so may give a zero reading when hazardous concentrations are present.
The user must apply correction factor if the substance is known

22. Escape Guidelines
Every facility or operations site that has the potential for H2S Exposure should have an emergency response plan
All personnel working in such a location should
Know the alarm system
Know where the potential sources are located
Know the wind direction
Know where safe zones and muster points are located
Know the evacuation routes
Know where emergency respirators are located

23. GENERAL FIRST AID CONSIDERATIONS
H2S First Aid
GENERAL FIRST AID CONSIDERATIONS
Fresh air ! (Rescuers must exercise caution!)
If unconscious/not breathing – immediately provide rescue breathing.
Call a doctor ASAP!
Give oxygen after cleaning oil from the injured employee’s face.

24. Summary Summary Stay out – Stay alive
Acute Risk: Moderate to high – respiratory failure, cardiac and neurological damage, ocular irritation
Small range of significant effects – many will tolerate 50 ppm; some fatalities, many injuries at 500 ppm
Odour not dependable to detect; use meters, detectors
Use air supplied respirators for rescue; Provide O2 / CPR
Explosive, may collect in low areas
Exposure concentrations may change without warning when low ventilation rates exist
Stay out – Stay alive
In summary, the acute risks are real. The margin of safety between levels that can easily exist and levels that result in fatalities is small.
Our ability to detect H2S by odor is not dependable but meters and detectors if calibrated and not damaged give us reliable information.
Control of exposure levels is very difficult due to unanticipated releases. These releases could put us into hazardous situations very rapidly. This is particularly true in low areas with poor ventilation.
Rescue teams must be particularly aware of hazards and use approved self contained respiratory protection.
Any questions?

25. H2S NEVER FORGET THAT HYDROGEN SULPHIDE IS A DEADLY GAS.
TAKE NO CHANCES WITH IT!
KNOW WHAT CONCENTRATION OF THE GAS IS PRESENT BEFORE DOING ANY WORK IN IT.

26. Properties and characteristics of H2S
The potential hazard of H2S is death
Detection of H2S solely by smell is highly dangerous as the sense of smell is quickly paralyzed by the gas.
Extremely toxic, ranking second to hydrogen cyanide and 5 to 6 times more toxic than carbon monoxide.
Colourless gas in its pure state
Offensive odour
Heavier than air – vapor density is (Air = 1.0) Vapours may travel considerable distance to a source of ignition and flashback. Sulfur dioxide is almost twice as heavy as air.
Forms an explosive mixture with air in concentrations between 4.6% LEL and 46% UEL

27. Properties and characteristics of H2S
Has an auto-ignition temperature of 500°F, Cigarettes burn at 1400°F
Burns with a blue flame and produces sulfur dioxide which is less toxic than H2S but highly irritation to eyes and lungs and can cause serious injury.
Soluble in water and liquid hydrocarbons. H2S dissolves in water forming a weak hydro-sulfurous acid.
Irritating to the eyes, throat and the respiratory system.
Corrosive to metals. H2S is also corrosive to plastics, elastomers, animal tissue and nerves
In certain applications, can form a pyrophoric substance called Iron Sulfide or Iron Sponge. This substance will auto-ignite when exposed to air.

28. DO NOT RELY SOLELY ON THE SENSE OF SMELL!
H2S Warning signs
Its odour is NOT a reliable warning signal because
higher concentrations of the gas temporarily destroys the sense of smell. This is the primary reason for employees not detecting the presence of H2S and consequently inhaling a lethal amount. The only positive means is by testing with an approved H2S detector.
DO NOT RELY SOLELY ON THE SENSE OF SMELL!