ST-7.24 H2S Safety

ST-7.24 H2S Safety REV DATED APPROVAL 01 01-04-2013 VP (HSEQ)

“No hazards down here mate! 11 20 04 P.A.W.S for thought “No hazards down here mate!

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

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 7783-06-4.

Concentration Levels & Effects Health Effects 10 ppm Beginning eye irritation 50-100 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 15-30 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 200-300 ppm Severe respiratory tract irritation after 1 hour of exposure. Possible pulmonary edema (fluid in the lungs). 500-700 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.

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

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)

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?

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.

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.

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

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.

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

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

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

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

Hydrogen Sulphide (H2S) Detection Zero Maintenance Sensor Range 0-100 ppm Low Alarm 10 ppm High Alarm 15 ppm -40 to +50 C

Multigas detector

Colourmetric indicator tubes There are 11 different H2S detector tubes available for H2S. Recommended Tube is: Drager Hydrogen Sulphide 2/b Tubes Range: 1 - 60 ppm Drager 8101961 Detector Tubes

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

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

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.

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?

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.

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 1.189 (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

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.

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!