Hydrogen Sulfide is naturally generated in situ from reservoir biomass and sulfate containing minerals through microbial sulfate reduction and thermochemical sulfate reduction. Produced from the decay of organic materials, it is found naturally in many mine sites. It is a part of volcanic gases, some mineral waters and unrefined carbonaceous fuels, such as natural gas, crude oil, and coal. Further to this, H2S can occur in the refining process as a by-product of oil and gas production.
What is Hydrogen Sulfide?
Chemical Compound: H2S
Hydrogen Sulfide is a colourless, poisonous gas with a sweet taste. It is often referred to by miners as ‘stinkdamp’ due to its pungent odour, resembling rotten eggs.
Safety Hazards of Hydrogen Sulfide
Health Effects of Hydrogen Sulfide Exposure
Hydrogen Sulfide is exceptionally hazardous, due to its high levels of flammability and toxicity. Personnel should be aware of the potential risks, hazard assessment, and related actions to ensure their safety.
Personnel are exposed to Hydrogen Sulfide most often during the drilling and production of natural gas, crude oil and petroleum products. Additional contact can occur in refineries, oil and gas wells, battery stations and pipelines as well as the transportation of fluids in which H2S is dissolved.
Due to its heavy density relative to the typical composition of air, the gas tends to pool and stagnate in wells and poorly ventilated areas. Universal occupational exposure limits are set out to eliminate any risk of adverse health effects.
Exposure Standard Details
|Standard Name||Hydrogen Sulfide|
|Time Weighted Average (parts per million)||10|
|Time Weighted Average (mg/m3)||14|
|Short Term Exposure Limit (parts per million)||15|
|Short Term Exposure Limit (mg/m3)||21|
Prolonged exposure to the gas has significant long-term side effects on our health and in extreme cases be fatal. As exposure increases, irritation occurs to the nose, throat, lungs and eyes before disturbing the nervous system; in turn causing headaches, vomiting and dizziness. Extreme exposure levels produce anoxia, the absence of oxygen in arterial blood and tissues, paralysing the respiratory system and ultimately resulting in death.
Hydrogen Sulfide Flammability
Hydrogen Sulfide is a highly flammable and explosive gas; flames can easily flashback to the source of a leak. H2S can travel considerable distances, forming explosive mixtures in the air in the range of approximately 4.5 - 45%.
Hydrogen Sulfide Monitoring Systems
The strong odour of Hydrogen Sulfide can be detected by smell concentrations as low as 1ppm; however, as an alert system this is an extremely unreliable method and should not be used.
Gas monitoring is predominant throughout mining. There are some devices available to detect the concentration of H2S and other gases within the atmosphere. Hydrogen Sulfide can be measured using a gas detector fitted with electrochemical sensors or by using indicator stain tubes.
Electrochemical sensors measure gas levels by measuring currents; the required gas undergoes a chemical reaction, producing a current directly proportional to the concentration of gas present in the atmosphere.
Fixed gas monitors measure gas concentration levels throughout a mine site or building. These site-wide warning systems relay data from a particular area to the control room and across the safety network. If abnormalities in gas levels are detected, automatic alerts and safety measures are activated. Fixed systems can have the ability to remotely shut down an area, isolating the hazard and ensuring the safety of all personnel in the event of an emergency.
Personal portable gas monitors provide the flexibility to be carried throughout the site. If gas levels are detected as outside acceptable levels, alert systems are activated, and individuals can take immediate appropriate action– reducing risk before it occurs.
Aura-FX Sensor Technology
In a refuge chamber, the Aura-FX Hydrogen Sulfide Monitor measures H2S levels; ensuring it remains within a safe range of below 10ppm. The sensor emits an initial warning signal at 5ppm, with an alarm sounding when levels reach 10ppm.
The monitor utilises an electrochemical gas sensor that measures the concentration of H2S by oxidising it at an electrode and then measuring the resulting current. The sensor has a read range from 0-50ppm. Calibration and sensor replacement are both required just once every 12 months.