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Anonymous asked in Science & MathematicsChemistry · 1 decade ago

can u give the explanation about h2s,forms, hazadous?

4 Answers

  • Anonymous
    1 decade ago
    Favourite answer

    It's the gas that rotten eggs smell of.It is used in ,so called,stink bombs.It is a deadly poison in very small concentrations but fortunately it's not likely to damage the general public because most sane people will try hard to escape the stink.

    It forms in oil wells and carboniferous rocks like limestone because they were formed from the trillions of trillions of small lifeforms hundreds of millions of years ago when the rocks and oil first started to form.

    If you break a piece of limestone rock and sniff the broken surface straight away, you will get the rotten egg whiff that been their since some little invertebrate died yonks ago.

  • ?
    Lv 7
    1 decade ago

    I hope you're ready for this...

    *..H2S is found in most crude oils and natural gas.

    At atmospheric temperature and pressure, it is a gas and has a very bad odour - like rotten eggs. H2S is highly toxic and is a 'Sour' or 'Acid' gas.

    *..Major Hazards:

    *..H2S is a flammable, toxic, and acid gas, which irritates the eyes and mucous membranes at concentrations between 20 to 150 ppm. Slightly higher concentrations cause irritation to the upper respiratory tract.

    *..Inhalation of 500 ppm for 30 minutes causes headaches, dizziness, excitement, and gastric disorders.

    *..Concentrations above 600 ppm can be fatal within 30 minutes due to respiratory paralysis.

    *..Smell alone cannot be relied upon to detect the presence of H2S, due to the paralyzing effect, it has on the olfactory nerves. The gas destroys the sense of smell at low concentrations.

    *..The Maximum allowable concentration in air is 10 ppm.

    *..Preventative Measures and Safety Precautions.

    1. Any area where the gas is likely to be met should be clearly marked with a - 'DANGER - H2S' Sign.

    2. Prevent any escape of the gas to atmosphere.

    3. Maintain good ventilation.

    4. Where H2S is likely, continuous detection and monitoring equipment should be installed and emergency oxygen supplies readily available.

    *..Emergencies. If H2S escapes to the atmosphere: -

    Stay upwind of the leak.

    Leave the area immediately.

    Use breathing apparatus if necessary.

    *..Iron Sulphide ( FeS )

    When moisture is present, and as little as 10% oxygen, H2S will react with the iron (Fe) of piping and equipment to form a 'Pyrophoric Compound' called 'Iron Sulphide' (FeS).

    'Pyrophoric' means 'Self Igniting'. FeS, in contact with the air, reacts with the oxygen. The reaction is 'Exothermic' - Gives out heat. The heat produced by the reaction in thick layers of ‘FeS’ or in discarded heaps, can become high enough to cause ‘Spontaneous Combustion ' (can be seen by a red glow of heat), which can lead to a fire if combustible materials are nearby.

    (Thin layers of FeS, as may be found in tanks or piping, may not actually cause too much heat build up due to the metal conducting away the heat produced).

    *..Where Pyrophoric iron is present, simply keeping it wet with water will prevent heat build up. However, if the material is allowed to dry out, it will again become dangerous.

    *..H2S also reacts with the metal (iron) of pipe-work and vessels and free hydrogen ions (H+), are formed which, due to their very tiny particle size, they can penetrate the walls of the metal and build up in tiny pockets created by the metal rolling process used to produce the metal. The ions combine within these pockets and, because they form hydrogen (H2) molecules, they become too large to exit the metal and remain in the pockets.

    *..This build up of high pressure hydrogen in the pockets causes 'Hydrogen Blistering'...(the pipe walls bulge outwards and inwards). These blisters actually cause weak spots in the metal and make it liable to rupture under the high pressure of Hydrogen thus produced in the pockets, with possible rupture and explosion of the pipeline itself.

    Source(s): This is NOT from any's from my notes made during my many years in the Oil & Gas Industry.
  • 1 decade ago

    h2s is deadly. 1 part in 9 billion can kill u. the thing is the first thing that goes is your sense of smell after that you lose consciousness and die. it is naturally produced in oil/gas

    Source(s): offshore worker who deals with this every day
  • 1 decade ago

    Small amounts of hydrogen sulfide occur in crude petroleum but natural gas can contain up to 90%. Volcanoes and hot springs emit some H2S, where it probably arises via the hydrolysis of sulfide minerals, i.e. MS + H2O to give MO + H2S. Normal concentration in clean air is about 0.0001-0.0002 ppm.[citation needed]

    Sulfate-reducing bacteria obtain energy by oxidizing organic matter or hydrogen with sulfates, producing H2S. These microorganisms are prevalent in low-oxygen environments, such as in swamps and standing waters. Sulfur-reducing bacteria (such as Salmonella) and some archaea obtain their energy by oxidizing organic matter or hydrogen with elemental sulfur, also producing H2S. Other anaerobic bacteria liberate hydrogen sulfide when they digest sulfur-containing amino acids, for instance during the decay of organic matter. H2S-producing bacteria also operate in the human colon, and the odor of flatulence is largely due to trace amounts of the gas. Such bacterial action in the mouth may contribute to bad breath. Evidence exists that hydrogen sulfide produced by sulfate-reducing bacteria in the colon may cause or contribute to ulcerative colitis.

    About 10% of total global emissions of H2S are due to human activity. By far the largest industrial route to H2S occurs in petroleum refineries: the hydrodesulfurization process liberates sulfur from petroleum by the action of hydrogen. The resulting H2S is converted to elemental sulfur by partial combustion via the Claus process, which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include coke ovens, paper mills (using the sulphate method), and tanneries. H2S arises from virtually anywhere where elemental sulfur comes into contact with organic material, especially at high temperatures.

    Hydrogen sulfide can be present naturally in well water. In such cases, ozone is often used for its removal. An alternative method uses a filter with manganese dioxide. Both methods oxidize sulfides to less toxic sulfates.

    A buildup of hydrogen sulfide in the atmosphere could have caused the Permian-Triassic extinction event 252 million years ago

    Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. The toxicity of H2S is comparable with that of hydrogen cyanide. It forms a complex bond with iron in the mitochondrial cytochrome enzymes, thereby blocking oxygen from binding and stopping cellular respiration. Since hydrogen sulfide occurs naturally in the environment and the gut, enzymes exist in the body capable of detoxifying it by oxidation to (harmless) sulfate.[4] Hence low levels of sulfide may be tolerated indefinitely. However, at some threshold level, the oxidative enzymes will be overwhelmed. This threshold level is believed to average around 300-350 ppm. Many personal safety gas detectors are set to alarm at 10 PPM and to go into high alarm at 15 PPM (Utility, sewage & petrochemical workers).

    An interesting diagnostic clue of extreme poisoning by H2S is the discoloration of copper coins in the pockets of the victim. Treatment involves immediate inhalation of amyl nitrite, injections of sodium nitrite, inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy.

    Exposure to lower concentrations can result in eye irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness. Chronic exposures to low level H2S (around 2 ppm) has been implicated in increased miscarriage and reproductive health issues amongst Russian and Finnish wood pulp workers, but the reports hadn't (as of circa 1995) been replicated. Higher concentrations of 700-800 ppm tend to be fatal.

    0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide [1], normally described as resembling "a rotten egg".

    10-20 ppm is the borderline concentration for eye irritation.

    50-100 ppm leads to eye damage.

    At 150-250 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger,

    320-530 ppm leads to pulmonary edema with the possibility of death.

    530-1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing;

    800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure(LC50).

    Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.

    A practical test used in the oilfield industry to determine whether someone requires overnight observation for pulmonary edema is the knee test: if a worker that gets "gassed" loses his balance and at least one knee touches the ground, the dose was high enough to cause pulmonary edema

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