H2S Hazards, Classification and Access Control Physiological Properties H2S has acute effects on people, as follows: Level of Concern H2S concentration in air Unpleasant Odour 0.13 ppm 8 Hour Threshold Limit Value (TLV) 5 ppm Immediately Dangerous to Life and 100 ppm Health (IDLH) Onset of significant health effects 300 ppm Immediate unconsciousness, onset of 650 ppm worker fatalities NOTE: 1% H2S equates to 10,000 ppm Physical Properties of H2S H2S is extremely toxic and can cause death at very low concentrations H2S, also known as sour gas, is a colourless toxic, corrosive and flammable gas, which is heavier than air and tends to collect in low-lying areas such as trenches, sumps and confined spaces. H2S reacts with the internal surfaces of carbon steel vessels in the absence of oxygen to form pyrophoric iron sulphide. Pyrophoric iron sulphide can when exposed to air. Property Characteristic Colour Colourless Odour H2S concentration, when: <100 ppm - has a distinctive, offensive smell similar to rotten – eggs >100 ppm - impairs the sense of smell; therefore, the nose cannot be relied upon to detect the presence of H2S Vapour Density 1.189 heavier than air – Explosive limits 4.3 to 46 percent by volume in air – and flammability H2S explodes over a very wide range, when: mixed in the right proportions with air (oxygen), and there is a source of ignition. Burns readily (with a distinctive blue flame) Produces Sulphur Dioxide (SO2) another toxic gas – Auto Ignition 260ºC Temperature Reactivity Can react with carbon steel, in the absence of oxygen forming – Pyrophoric Iron Sulphide (on the internal surfaces of vessels), which in turn can react upon contact with air (oxygen) auto igniting –
H2S Hazards, Classification and Access Control Physiological Properties H2S has acute effects on people, as follows: Level of Concern H2S concentration in air Unpleasant Odour 0.13 ppm 8 Hour Threshold Limit Value (TLV) 5 ppm Immediately Dangerous to Life and Health (IDLH) 100 ppm Onset of significant health effects 300 ppm Immediate unconsciousness, onset of worker fatalities 650 ppm NOTE: 1% H2S equates to 10,000 ppm Physical Properties of H2S H2S is extremely toxic and can cause death at very low concentrations H2S, also known as sour gas, is a colourless toxic, corrosive and flammable gas, which is heavier than air and tends to collect in low-lying areas such as trenches, sumps and confined spaces. H2S reacts with the internal surfaces of carbon steel vessels in the absence of oxygen to form pyrophoric iron sulphide. Pyrophoric iron sulphide can when exposed to air. Property Characteristic Colour Colourless Odour H2S concentration, when: <100 ppm - has a distinctive, offensive smell – similar to rotten eggs >100 ppm - impairs the sense of smell; therefore, the nose cannot be relied upon to detect the presence of H2S Vapour Density 1.189 – heavier than air Explosive limits and flammability 4.3 to 46 percent – by volume in air H2S explodes over a very wide range, when: mixed in the right proportions with air (oxygen), and there is a source of ignition. Burns readily (with a distinctive blue flame) Produces Sulphur Dioxide (SO2) – another toxic gas Auto Ignition Temperature 260ºC Reactivity Can react with carbon steel, in the absence of oxygen – forming Pyrophoric Iron Sulphide (on the internal surfaces of vessels), which in turn can react upon contact with air (oxygen) – auto igniting
PR-1078%20-%20Hydrogen%20Sulphide%20Management%20Procedure.docx