Hydrogen Sulfide or sour gas (H2S) is a flammable, colorless gas that is toxic at extremely low concentrations. It is heavier than air, and may accumulate in low-lying areas. It smells like "rotten eggs" at low concentrations and causes you to quickly lose your sense of smell. Many areas where the gas is found have been identified, but pockets of the gas can occur anywhere.
Iron sulfide is a byproduct of many production operations and may spontaneously combustion with air.Flaring operations associated with H2S production will generate Sulfur Dioxide (S02), another toxic gas.
Active monitoring for hydrogen sulfide gas and good planning and training programs for workers are the best ways to prevent injury and death.
Hydrogen Sulfide gas is very corrosive and causes metals to become brittle. Therefore, employers need to take special precautions when choosing equipment when they may reasonably expect to encounter H2S. This may include appropriate H2S trimming of equipment in accordance with National Association of Corrosion Engineers (NACE) Standards.
All well-drilling sites should be classified according to areas of potential and/or actual exposure to H2S. The recommendations and employee instruction will vary depending on the type of area. The four hazard levels are:
Any well that will not penetrate a known Hydrogen Sulfide formation would be categorized as a No Hazard Area. Special Hydrogen Sulfide equipment is not required.
Work locations where atmospheric concentrations of H2S are less than 10ppm.
Recommended for Area:
Work locations where atmospheric concentrations of H2S are greater than10ppm and less than 30ppm.
Recommended for Area:
Work locations where atmospheric concentrations of H2S are greater than 30ppm.
Recommended for Area:
All personnel working in an area where concentrations of Hydrogen Sulfide may exceed the 10 Parts Per Million (PPM) should be provided with training before beginning work assignments.
Potential Hazard:
Possible Solutions:
Implement an H2S contingency plan including, but not limited to:
Metal fatigue, including hydrogen embrittlement or sulfide stress cracking, can result in a release of hydrogen sulfide gas.
Potential Hazard:
Possible Solutions:
It is possible for hydrogen sulfide gas to accumulate in any low /enclosed area,such as a gas venting system, mud system, cellars, pits, and tanks.
Potential Hazard:
Possible Solutions:
The American Conference of Governmental Industrial Hygienists recommends a Threshold Limit Value of 1 ppm and a short-term exposure (STEL) limit of 5 ppm averaged over 15 minutes. Exposure at the STEL should not be repeated more than four times per day with at least 60 minutes between successive exposures in this range.
Inhalation at certain concentrations can lead to injury of death. The 300 ppm is considered by the ACGIH as Immediately Dangerous to Life and Health. Hydrogen sulfide is an extremely toxic, flammable gas that may be encountered in the production of gas well gas, high-sulfide, high sulfur content crude oil, crude oil fractions, associated gas, and waters. Since hydrogen sulfide is heavier than air, it can collect in low places. It is colorless and has a foul rotten egg odor. In low concentrations, H2S sometimes can be detectable by its characteristic odor; however, the smell cannot be relied upon to forewarn of dangerous concentrations (greater than 100ppm) of the gas because it rapidly paralyzes the sense of smell due to paralysis of the olfactory nerve. A longer exposure to the lower concentrations has a similar desensitizing effect on the sense of smell.
It should be well understood that the sense of smell will be rendered ineffective by hydrogen sulfide, which can result in an individual failing to recognize the presence of dangerously high concentrations. Exposure to hydrogen sulfide causes death by poisoning the respiratory system at the cellular level. Symptoms from repeated exposures to low concentrations usually disappear after not being exposed for a period of time. Repeated exposures to low concentrations that do not produce effects eventually may lead to irritation if the exposures are frequent.
Respiratory protection shall be worn above the action level. Refer to 6.6 for proper breathing equipment recommendations for oil and gas well drilling and servicing operations involving hydrogen sulfide.
Before handling, it is important that all engineering controls are operating and that protective equipment requirements and personal hygiene measures are being followed. Only trained personnel should work with this product. Do NOT work alone with this product. In event of a spill or leak, immediately put on escape-type respirator and exit the area. Use non-sparking ventilation systems, approved explosion-proof equipment and intrinsically safe electrical systems. Electrically bond and ground equipment. Ground clips must contact bare metal. Eliminate heat and ignition sources such as sparks, open flames, hot surfaces and static discharge. Post "No Smoking" signs. Prevent accidental contact with incompatible chemicals. Use the pressure regulator appropriate for cylinder pressure and contents. Secure cylinder in an up-right position. Protect cylinders from damage. Use a suitable hand truck to move cylinders; do not drag, roll, slide, or drop.
Store in an area that is: cool, dry, temperature-controlled, well-ventilated, out of direct sunlight and away from heat and ignition sources, separate from incompatible materials, an approved, fire resistant area, clear of combustible and flammable materials (e.g. old rags, cardboard), on the ground floor or preferably, in an isolated, detached building. Electrically bond and ground containers. Ground clips must contact bare metal. Avoid bulk storage indoors. Empty containers may contain hazardous residue. Store separately. Keep closed.
Evacuate the area immediately. Isolate the hazard area. Keep out unnecessary and unprotected personnel. Evacuate downwind locations.
Liquid: stop or reduce leak if safe to do so. If not, allow liquid to vapourize. Ventilate the area to prevent the gas from accumulating, especially in confined spaces. Gas: stop or reduce leak if safe to do so. Ventilate the area to prevent the gas from accumulating, especially in confined spaces.
Main Routes of Exposure: Inhalation; eye contact.
Inhalation:VERY TOXIC, can cause death. Can cause severe irritation of the nose and throat. Can cause life threatening accumulation of fluid in the lungs (pulmonary edema). Can cause, excitement, headache, dizziness, staggering, sudden collapse ("knockdown"), unconsciousness, and death Long-term damage may result from a severe short-term exposure. Can harm the nervous system. Can cause lung injury. A single exposure to a high concentration can cause a long-lasting condition like asthma. If this occurs, many things like other chemicals or cold temperatures can easily irritate the airways. Symptoms may include shortness of breath, tightness in the chest and wheezing. {Reactive Airways Dysfunction Syndrome (RADS)}.
Direct contact with the liquefied gas can chill or freeze the skin (frostbite).Symptoms of mild frostbite include numbness, prickling and itching. Symptoms of more severe frostbite include a burning sensation and stiffness. The skin may become waxy white or yellow. Blistering, tissue death and infection may develop in severe cases.
EYE IRRITANT. The gas irritates the eyes. Direct contact with the liquefied gas can freeze the eye. Permanent eye damage or blindness can result.
Ingestion:Not a relevant route of exposure (gas).
Conclusions cannot be drawn from the limited studies available. May harm the nervous system. Symptoms may include restlessness, reduced ability to think, muscle tremors, memory loss and personality changes. May harm the respiratory system.
Carcinogenicity: Not known to cause cancer.
Take precautions to prevent a fire (e.g. remove sources of ignition). Take precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment). Move victim to fresh air. Keep at rest in a position comfortable for breathing. If breathing is difficult, trained personnel should administer emergency oxygen. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema may be delayed. If breathing has stopped, trained personnel should begin artificial respiration (AR). If the heart has stopped, trained personnel should start cardiopulmonary resuscitation (CPR) or automated external defibrillation (AED). Avoid mouth to mouth contact by using mouth guards or shields. Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
NOTE: Victims may pose a threat to responders due to the release of hydrogen sulfide from their clothing, skin, and exhaled air.
Liquefied gas: quickly remove victim from source of contamination. DO NOT attempt to rewarm the affected area on site. DO NOT rub area or apply direct heat. Gently remove clothing or jewelry that may restrict circulation. Carefully cut around clothing that sticks to the skin and remove the rest of the garment. Loosely cover the affected area with a sterile dressing. DO NOT allow victim to drink alcohol or smoke. Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital. Double bag, seal, label and leave contaminated clothing, shoes and leather goods at the scene for safe disposal.
Gas: immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 15-20 mint, while holding the eyelid(s) open. Liquefied gas: immediately and briefly flush with lukewarm, gently flowing water. DO NOT attempt to rewarm. Cover both eyes with a sterile dressing. DO NOT allow victim to drink alcohol or smoke. Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
Ingestion: Not applicable (gas).
Some of the first aid procedures recommended here require advanced first aid training. All first aid procedures should be periodically reviewed by a doctor familiar with the chemical and its conditions of use in the workplace.
Persons not wearing protective equipments and clothing should be restricted from areas of spill or leaks until cleanup has been completed.
If hydrogen sulfide i spilled or leaked, the folowing steps should be taken,
1. Remove all ignition sources.
2. Ventilate the area of spill or leak to disperse gas.
3. If in the gaseous form, stop flow of gas. If the source of leak is a cyliner and the leak can not be stopped in place, remove the leaking cylinder to a safe place in the open air, and repair the leak or allow the cylinder to empty.
4. If in the liquid form, allow to vaporize.
Use a local exhaust ventilation and enclosure, if necessary, to control amount in the air. It may be necessary to use stringent control measures such as process enclosure to prevent product release into the workplace. Use non-sparking ventilation systems, approved explosion-proof equipment and intrinsically safe electrical systems in areas where this product is used and stored. Use a ventilation system separate from other exhaust ventilation systems. Filter the contaminated air before it is directly exhausted to the outside. Use leak and fire detection equipment and an automatic fire suppression system.
Click the below link to download hydrogen sulfide guidelines documents
Safety guidelines - Hydrogen sulfide
Power point presentation-1- Hydrogen sulfide
Power point presentation-2- Hydrogen sulfide
OSHA Quick card - Hydrogen sulfide
Tool box talk - Hydrogen sulfide awareness
