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H2S Overview

H2S can be found on many jobsites, not just those connected with the petroleum industry. It may accumulate wherever a mixture of hydrocarbons and sulphur are found. Oil and gas fields, tankers and production facilities all have the potential to contain significant amounts of the gas.

Besides these locations, there are a variety of organic sources where H2S can be found. This includes such unlikely spots as ship’s holds, mine shafts, pulp mills, swamps, and sewers. H2S is a natural by-product of organic decay.

All petroleum industry jobsites are potential locations of the gas. To predict likely locations of H2S, you first need to be aware of the physical properties of the gas itself. What it is like and how it behaves provide general clues about potentially hazardous situations. This type of information can then be used to avoid exposure, injury and possible death.

Physical Properties 

The properties of all gases are usually described in the context of seven major categories:

• Colour
• Odour
• Vapour Density
• Explosive Limits
• Flammability
• Solubility (in water)
• Boiling point

Hydrogen Sulfide is no exception. Information from all of these categories should be considered to provide a fairly complete picture of the physical properties of the gas.


H2S is colourless so it’s invisible. This fact simply means that you can’t rely on your eyes to detect its presence; this makes the gas extremely dangerous to be around.


H2S has a distinctive offensive smell, similar to “rotten eggs”. For this reason it earned its common name, “sour gas”. H2S even in low concentrations is so toxic that it attacks and quickly impairs a victim’s sense of smell, so it could be fatal to rely on your nose as a detection device.

Vapour Density 

Hydrogen Sulfide is heavier than air so it tends to settle in low lying areas like pits, cellars, or tanks. If you find yourself in a location where H2S is known to exist, protect yourself. Whenever possible, work in an area upwind and keep to higher ground.

Explosive Limits 

Mixed with the right proportion of air or oxygen, H2S will explode, presenting another alarming element of danger besides potential poisoning.


H2S will burn readily with a distinctive blue flame, producing Sulphur Dioxide (SO2); another hazardous gas that irritates the eyes and lungs.


The gas can be dissolved in liquids, which means that it may be present in any container or vessel used to carry or hold well fluids including oil, water, emulsion and sludge. The solubility of H2S idependst on temperature and pressure, but if conditions are right, simply agitating a fluid containing H2S may release the gas into the air.

Boiling Point 

Liquefied H2S boils at a very low temperature which is why it is usually found as a gas.


These seven physical properties of Hydrogen Sulfide provide a general profile of the characteristics of the gas. Using this information you can make general predictions about where the gas might be found and this should help you avoid exposure to H2S gas.

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Sabre Safety Ltd.

Sabre Safety Services Ltd. Dundee
Strathmore House, Charles Bowman Avenue, Claverhouse Industrial Park, Dundee DD4 9UB
Tel: +44 (0)1382 214981
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