Hydrogen sulphide guide
Find out more about the gas hydrogen sulphide, its chemical and physical properties, its occurrence and the various areas of application in the hydrogen sulphide guide. Due to the highly dangerous nature of the gas, which is comparable to hydrogen cyanide, the hydrogen sulphide guide is dedicated to the risks, first aid measures and correct behaviour in hazardous areas.
- Properties of hydrogen sulphide
- Toxicity of hydrogen sulphide
- Hydrogen sulphide in the organism
- Natural formation of hydrogen sulphide
- Utilisation of hydrogen sulphide
- Health hazards due to hydrogen sulphide
- Typical symptoms of poisoning with hydrogen sulphide
- First aid measures in the event of contact
- Safe handling of hydrogen sulphide
- Storage conditions
- Methods for the detection of hydrogen sulphide
Properties of hydrogen sulphide
Hydrogen sulphide is a highly toxic gas for humans and animals with the foul odour typical of sulphur compounds, which is reminiscent of rotten eggs and is perceptible even at very low concentrations. However, one should not really rely on the human nose. Hydrogen sulphide quickly leads to odour blindness and can no longer be smelled when it becomes really dangerous. Hydrogen sulphide is also known as hydrogen sulphide, dihydrogen sulphide hydrogen sulphide, hydrogen sulphide acid, hydrothionic acid, hydrogen sulphide, sulfan, monosulfan.
The molecules of the gas with the molecular formula H2S and the molecular structure H-S-H (bond angle 92.25°) consist of two atoms of hydrogen and one atom of sulphur. It is colourless, flammable, highly flammable and corrosive. The ignition temperature of hydrogen sulphide is 270° C. At 100.1° C, the gas reaches the critical temperature and the critical pressure at 89.37 bar. The lower explosion limit is 3.9 % vol. The OEL (EU recommendation) is 5 ppm (short-term value 10 ppm).
The solubility in water is moderate at 0.539 g at 10° C and 0.398 g at 20° C, but increases strongly with increasing pH value from 9. The aqueous solution obtained by dissolution in water is a dibasic weak acid with a pKs value of 7.05.
With a molar mass of 34.08 g/mol, hydrogen sulphide has a slightly higher density than air. As a result, the gas accumulates in deeper areas in poorly ventilated rooms.
Hydrogen sulphide in aqueous solution reacts with various heavy metal salts. For example, it reacts with lead(II) ions to form black lead sulphide and with iron(II) ions to form black iron sulphide. In each case, these are insoluble sulphides. Due to this reactive property, simple detection using lead acetate paper is possible as soon as sulphur compounds or products containing sulphur compounds are heated.
Hydrogen sulphide also reacts with numerous chemicals. The consequences of contact can be a generally dangerous reaction or an explosion.
Toxicity of hydrogen sulphide
This dangerous gas has a toxic effect on the body in several ways.
If it comes into contact with mucous membranes and tissue fluids, hydrogen sulphides are formed with a strong irritant effect. Therefore, one of the first symptoms is irritation of the eyes. Depending on the severity of the poisoning, water retention, such as pulmonary oedema, is another consequence of more severe exposure.
However, hydrogen sulphide also has a destructive effect, as it binds to the haemoglobin active in the blood within a short time after ingestion of the gas via the respiratory tract. As haemoglobin is necessary for the transport of oxygen into the cells, the cells are undersupplied with oxygen, resulting in damage to health.
Hydrogen sulphide in the organism
Hydrogen sulphide is found in many places in nature. This includes the human organism, in which the gas fulfils important functions despite its high toxicity for humans and animals.
In addition to nitric oxide, which is a messenger substance that triggers relaxation of the vascular muscles, hydrogen sulphide is another gasotransmitter that has been detected in mammals and in the human organism. The gas is produced by the enzyme cystathionine-gamma-lyase (CSE) as a blood pressure regulating substance by contributing to vasodilatation. This effect was demonstrated in animal experiments by breeding mice without a functional CSE gene. Measurements of the hydrogen sulphide content in the blood vessel system and in the tissue showed that the animals with the defective gene had a significantly lower hydrogen sulphide content. At the same time, the blood pressure in these animals was increased by up to 20 %.
However, hydrogen sulphide can also be found in other organs. For example, the gas is found in the erectile tissue of the penis and in the smooth muscles of the penile artery. Here it serves as a messenger substance that triggers vasodilation. Another organ in which the gas regularly forms as a result of digestive processes is the intestine. Last but not least, hydrogen sulphide, along with other volatile organic compounds containing sulphur, is responsible for unpleasant bad breath.
Natural formation of hydrogen sulphide
Hydrogen sulphide occurs very frequently in nature. It is produced in all decomposition and putrefaction processes of biomass. The gas is formed during the decomposition of animal carcasses as well as during the decomposition of leaves or the formation of sludge at the bottom of standing water. Other natural sources are volcanic gas, natural gas and crude oil.
Hydrogen sulphide is also found in numerous springs in dissolved form and in low concentrations. These springs have the typical unpleasant odour, but are not always hazardous to health. Sometimes the opposite is the case, when the dissolved gas in the spring water has a healing effect on skin diseases. This knowledge about healing springs is not new. People have been using healing springs for several centuries.
Particularly in areas where biomass decomposition takes place in large quantities and corresponding quantities of the gas are produced, hydrogen sulphide causes considerable damage to concrete structures and other technical components due to its corrosive properties. This applies, for example, to biogas plants, high-pressure wastewater pipes, landfill sites and slurry pits.
Utilisation of hydrogen sulphide
In the petrochemical industry, large quantities of hydrogen sulphide are produced during the desulphurisation of crude oil and natural gas. These are further processed in large-scale industry. Hydrogen sulphide is an important raw material for sulphur production. Most of the sulphur obtained in this way is then processed into sulphuric acid. Sulphuric acid is indispensable in numerous processes in the chemical industry.
Industrially, hydrogen sulphide is the raw material for compounds that are used to refine lubricants and in the production of pesticides or medicines. Hydrogen sulphide is used as a test or calibration gas in the manufacture of electronic components and in the photovoltaic industry.
In order to remove hydrogen sulphide from the biogas and digester gas plants as well as in waste water sewers, the gas is bound with iron(II) chloride to form insoluble iron sulphide and thus precipitated.
Health hazards due to hydrogen sulphide
Hydrogen sulphide is highly toxic to humans and is comparable to the toxicity of hydrogen cyanide. At high concentrations, the gas leads to death within a short time. Due to the hazardous nature of hydrogen sulphide, it is very important to be aware of where the dangerous gas is formed. Such hazardous areas can be the slurry pit, but also the freight container with dead animals.
Hydrogen sulphide is mainly absorbed via the respiratory tract. There is only a risk of oral ingestion when working with saturated aqueous hydrogen sulphide solution. Depending on the concentration of the gas in the inhaled air, the first symptoms may appear within a short time.
At low concentrations, eye irritation is one of the first symptoms. If you are exposed for a longer period of time or if the gas concentration increases, severe symptoms and even death will occur within a short time.
Typical symptoms of poisoning with hydrogen sulphide
- below 250 ppm: eye irritation, drowsiness, dizziness, nausea
- from 250 ppm: anaesthetisation of the odour receptors
- from 500 ppm: nausea, dizziness, cramps, unconsciousness
- from 1000 ppm: unconsciousness after a few breaths, respiratory paralysis, heart failure
- from 5000 ppm: death after a few seconds
If a person is exposed to a gas concentration of 500 ppm, life-threatening damage occurs. A few minutes at a concentration of 1000 ppm will lead to death without assistance. Unconsciousness occurs after just a few breaths.
To make the idea of the toxicity of the gas more tangible: 1000 ppm corresponds to 0.1 % gas content in the room or immediate ambient air.
Due to the intense and very unpleasant odour, the presence of hydrogen sulphide in the ambient air can be detected even at low concentrations, so that people can take appropriate action if they react immediately. This immediate reaction can be life-saving! This is because the anaesthetic effect of the gas on the odour receptors means that the odour is no longer perceived after a short time. This is particularly fatal if the concentration of the gas in the ambient air increases rapidly due to leaks in a container or a flow pipe.
First aid measures in the event of contact
In an emergency, first aid measures must be initiated immediately and an emergency call must be made to obtain medical assistance as quickly as possible. Pay attention to self-protection during all measures and wear the respiratory protection provided for such situations before entering the danger zone.
- Remove the injured person from the danger zone to fresh air as quickly as possible.
- Keep the injured person calm and protect them from hypothermia.
- If available, give pure oxygen.
- If the injured person has difficulty breathing, ensure that they are in a semi-sitting position.
- If the injured person is unconscious but still breathing on their own, place them in the recovery position and keep their airway open.
- If respiratory arrest occurs, use mechanical ventilation.
- In the event of circulatory arrest (no pulse, no breathing), start resuscitation measures in the form of chest compressions and ventilation.
- Use an available defibrillator for resuscitation measures, if one is available.
As soon as the doctor arrives, he receives all relevant information about the cause of the accident as well as the measured values of the gas concentration and the duration to which the injured person was exposed. Based on this information, the emergency doctor can immediately initiate the appropriate measures.
Safe handling of hydrogen sulphide
The handling of hydrogen sulphide must be carried out under the highest safety precautions and is only permitted for appropriately instructed persons. Regular measurements trigger an alarm if the room air is contaminated with the gas.
Personal protective equipment is of great importance.
- Chemical protection suit for emergencies
- Flame-retardant and antistatic protective clothing
- Safety shoes
- Safety gloves made from nitrile rubber or nitrile latex
- Safety goggles with side protection
For emergencies, you should always carry a breathing apparatus with gas filter B, identification colour grey. This will help to ensure your own safety in an emergency and allow you to remove yourself from the danger zone.
In an emergency, remember that hydrogen sulphide is heavier than air and can accumulate in the floor area, especially in poorly ventilated rooms. Therefore, do not enter depressions such as pits in the room or basement areas where the gas can accumulate without first checking the gas concentration. Always wear respiratory protection if hydrogen sulphide is present.
Storage conditions
As hydrogen sulphide is a hazardous substance, i.e. a potentially harmful gas for humans and the environment, great care must be taken when storing containers with hydrogen sulphide.
Due to the high flammability, storage should only take place in well-ventilated rooms with explosion protection equipment suitable for operation in a potentially hazardous explosive atmosphere. Oxidising gases and other oxidising substances must never be stored together with the hydrogen sulphide containers. As a safety measure against serious accidents, gas detectors with alarm triggering are also recommended in the storage room. At the very least, authorised employees should be equipped with a mobile gas detector with which they can take a measurement before entering the area.
Bottles in storage must be fitted with a valve protection cap or valve protection cage and checked at regular intervals for leaks in the fittings and for corrosion. As with all pressurised containers, the ambient temperature must remain below 50° C and direct sunlight on the products must be avoided at all costs.
If the gas is in a closed system, it is only operated under strictly controlled conditions. Ideally, the system should be permanently technically sealed with welded pipes. Safety valves are required by law. Like pressurised containers, closed systems must also be checked regularly for leaks.
As this is a storage room for toxic gases, a system for the safe discharge of escaping gas is required. It should be noted that the discharge system can be switched on remotely from a non-hazardous area, unless it is automatically activated via the gas detector.
Methods for the detection of hydrogen sulphide
Hydrogen sulphide anaesthetises the odour receptors after a short time. As a result, people no longer perceive the danger after a short time. This happens very quickly at higher concentrations, but also occurs at initially low exposures that continuously increase. As a result, there is a high risk of the situation being misjudged. Due to the great danger posed by hydrogen sulphide, measurements with specially developed measuring devices are essential in all areas with possible contamination. Hydrogen sulphide is best detected using devices equipped with electrochemical sensors.
Compur Monitors offers a range of powerful measuring devices for the detection of hydrogen sulphide as stationary solutions for continuous measurement. Mobile measuring devices enable employees to carry out a clearance measurement immediately before entering a hazardous area. As an expert in the development of gas detection devices, Compur Monitors has been one of the leading manufacturers of these devices, which are indispensable in many areas, for many years.
Dr. Josef von Stackelberg
Managing Director COMPUR MONITORS GmbH & Co. KG
Contact us without obligation
Do you have any questions about our products or would you like a non-binding consultation? We look forward to hearing from you.
