H2S HYDROGEN SULPHIDE GAS This course follows Guidelines for: OSHA 29 CFR 1910.1200, ANSI Z-390.1, ANSI Z490.1 and API - RP 49 & 55
Objectives of This Course • To Understand The Physical Properties of H2S • Understand the Hazards of H2S and SO2 • Understand Proper Working Procedures in an H2S environment • Understand H2S Detection • Understand the Contingency Plan • Understand Basic Rescue Techniques • Be Able to put on a Self Contained Breathing Apparatus • Pass a Written Examination
Where Does H2S Come From? • Same Place as Oil & Gas • Mining Industry • Tanning Industry • Paper Mills • Water Treatment Plants • Sewers • Septic Tanks • Chemical Factories
Different Names for the Same Thing H2S Hydrogen Sulphide Rotten Egg Gas Sour Gas Swamp Gas The Invisible Killer
Physical Properties Corrosiveness Solubility Flammability Boiling Point Toxicity Color Odor Density
Toxicity What does toxic mean? Poison! Something that harms our bodies. Do you understand parts per million (ppm)? If you consider a time span of 11 ½ days, one second is 1 ppm. 700 ppm of H2S is enough to kill you with one breath!
Target Organs Hydrogen sulfide is a toxic and irritant gas whose major effects are exerted on the nervous system, the eyes and the respiratory tract. Other target organs/body structures affected include the brain and olfactory nerves. Olfactory Nerves: Loss of sense of smell occurs within 3-5 minutes at 100 ppm Brain: Headaches, nausea, dizziness, confusion, brain damage
Target Organs Eyes: Irritation, tearing, inflammation, conjunctivitis, temporary loss of vision Respiratory Tract: Throat irritation, coughing, olfactory fatigue, pulmonary edema, respiratory arrest Nervous System: H2S in the bloodstream reduces the oxygen-carrying capability of the blood which depresses the nervous system. Immediate collapse from nervous system paralysis and respiratory arrest is usually followed within 5-10 minutes by cardiac failure.
Color What Color is Hydrogen Sulphide? You cannot use your eyes to detect H2S.
Odor What does H2S smell like? Can we use our nose to detect H2S? Can we depend on our nose to detect H2S? At 50-150 ppm concentration of H2S, we lose our sense of smell. H2S stops messages from traveling between the brain and the nerves, including the olfactory nerve (sense of smell).
Density Specific Gravity of Gas Ambient air at sea level is one atmosphere, or = 1.0 H2S = 1.189 H2S is about 19 % heavier than air. Collects in low areas Stacks or builds on itself.
Wind Direction How can we tell wind direction? Why is wind direction important in H2S safety? We need to be upwind of an H2S release. What if there is no wind? What do we mean by “Wind Conscious”?
WIND DIRECTION SOURCE OF H2S CONCENTRATION DECREASES FROM CENTER WHICH WAY TO GO? CONCENTRATION DECREASES AWAY FROM SOURCE GO CROSSWIND AND UPWIND!
Boiling Point What is boiling point? Boiling Point – the temperature at which a liquid turns into a gas. BP of H2O is 100º C, BP of H2S is - 60º C Why is this important to us?
Flammability H2S is highly flammable The auto-ignition temperature of H2S is 260º C A cigarette burns at a temperature of 400º C Burns with a bright blue flame Highly explosive, even more than Methane
Explosivity Explosivity Range LEL [------------------------------] UEL Lower Explosive Level Upper Explosive Level 4.3 % 46 % 43,000 ppm 460,000 ppm 1 % = 10,000 ppm
When we burn H2S we get a very toxic byproduct: Sulfur Dioxide
Sulfur Dioxide Toxicity – PEL – 5 ppm, IDLH – 100 ppm Color – none Odor – irritating pungent odor Specific Gravity (RGasD) – 2.26 (air = 1.0) Nonflammable Reacts with water to form sulfurous acid Symptoms of Exposure – eye, nose and throat irritation, choking, and coughing, suffocation
Why Burn H2S? No longer flammable or explosive The heated gases rise and are dissipated into the atmosphere
Solubility H2S is soluble in fluids At 0º C, 4 parts of gas can be retained in 1 part of water. (This is volumetric.) At 20º C, 2.6 parts of gas can be retained in 1 part water. What does this mean to us? How can we get gas out of solution?
Removing Gas from Fluids • Temperature Change • Agitation
Corrosiveness H2S is very corrosive It reacts with metals, plastics and rubber H2S dissolves in water to make a weak acid Can cause pitting in steel Can cause hydrogen embrittlement
Hazards and Symptoms • Effects Depend on Several Factors • Intensity- Concentration • Duration- Length of Time Exposed • Frequency- How Often You Are Exposed • Individual Susceptibility
ROUTES OF ENTRY AND TARGET ORGANS INJECTION: > Bloodstream INGESTION: > Stomach, Gastrointestinal Tract, Bloodstream, Liver ABSORPTION: > Bloodstream INHALATION: > Respiratory System, Bloodstream
Symptoms of Exposure Low Concentrations Irritation to eyes, nose and throat Moderate Concentrations Dizziness Headache Vomiting Loss of equilibrium High Concentrations
Loss of Consciousness Death
Toxicity Table for H2S ppm Physical Effects .013 Lower odor threshold (rotten eggs) 10 Possible Headache (PEL) 15 Mild nausea (STEL) 20 Possible fatigue (TLV-C) 50 Drowsiness 100 Loss of sense of smell in 2-15 minutes (cont’d)
Toxicity Table (Cont’d) ppm Physical Effects 200 Burning sensation in eyes, nose, throat and chest, stiffness in joints 300 IDLH level 500 Loss of equilibrium, loss of mental functions, respiratory disturbance 700 Rapid unconsciousness followed by Respiratory Arrest
OUTFLOW LINE AIR H2S STORAGE TANK IS 8 PPM H2S REALLY SAFE? DISPLACED AIR! H2S 8 PPM OUTFLOW OF HEAVIER THAN AIR H2S
Respiratory Protection Problems Encountered Facial Hair Corrective Spectacles Contact Lens Psychological Disturbances Discomfort Miscellaneous Sealing Problems
Respiratory Protection There are Three Types of Breathing Apparatus Rescue Units Work Sets Escape Sets
Respiratory Protection Use the Right Equipment for the Job!
Things to Consider When Providing Breathing Air • Air must be of acceptable quality • Air must be of adequate amount to do the job
Grade D Breathing Air Quality Requirements Water Vapor <=/50 Mg/M3 Carbon Monoxide <=/10 ppm Carbon Dioxide <=/500 ppm Oil Mist <=/.5 Mg/M3
How Much Breathing Air • The average person breathes approximately 1.5 cubic feet (40 liters) of air /min at medium work. • The same person breathes approximately 5 cubic feet (140 liters) of air per min. at maximum work.
A Five Minute Escape Set will be used up in less than Two Minutes when the user is under stress and performing heavy work.
Moral NEVERUSE AN ESCAPE SET TO ATTEMPT A RESCUE!
As a “Rule of Thumb”….. A worker at maximum stress and work will consume approximately 4.5 ft3 of breathing air per minute…
Detection and Monitoring • Two Ways of Monitoring Gas • Fixed Monitors • Portable Monitors
Two Ways of Monitoring Gas • Fixed Monitors • Portable Monitors
Fixed Monitors Continuously sensing for gas Controller placed for easy surveillance in control room Has fault indicators Can monitor remote areas Has warning systems attached Lights flash at 10 ppm - PEL Sirens sound at 15 ppm – STEL
Portable Monitors Continuously sensing for gas Controller placed for easy surveillance in control room Has fault indicators Can monitor remote areas Has warning systems attached Lights flash at 10 ppm - PEL Sirens sound at 15 ppm – STEL
When the Alarms Go Off • Hold your breath, put on BA if available • Move upwind of the leak, note wind direction • Evacuate to the “Safe Briefing Area” • Alert all persons on the way to the “SBA” • Report to your supervisor • Await further instructions • DO NOT PANIC
What is a false alarm? There is no such thing. There was a reason that the alarm sounded. What was it?
What is a Contingency Plan? It’s a, "What Are We Gonna Do, If " Plan
Where Do I Fit In? I have been assigned specific duties My only duty is to get to the briefing area Everyone has a job to do If you don’t do your job, we come looking for you If you don’t know your job, ASK. The only stupid question there is, is the one you didn’t ask
The Buddy System When the H2S alarm sounds, you never work alone. Minimum of 2 persons at all times. You always have someone in visual contact in case your equipment malfunctions. Your buddy can get help immediately if needed
Signs and Symptoms of Acute Toxicity Olfactory Paralysis Excitement Eye Irritation Coughing Headaches Sneezing Nausea Respiratory Irritation Diarrhea Pulmonary Edema Dizziness Respiratory Arrest Confusion Brain Damage Staggering Gait Photophobia Cardiac Arrest
Signs and Symptoms of Chronic Toxicity Eye Irritation Corneal Blistering, Pitting, Opacity Headaches Nausea Irritation of Respiratory Tract Pulmonary Edema Anorexia Sleep Disturbances