Hydrogen sulfide is colourless and has a characteristic “rotten egg” smell. It is an extremely dangerous gas. It is so damaging to the human nervous and respiratory systems that it was used as a chemical weapon in World War I.1
It’s highly poisonous, acting as both an irritant and a chemical asphyxiant (meaning it interferes with oxygen utilisation in the body) and effects can occur after a single breath.2 At low levels, exposure can result in eye irritation, coughing, nausea, and fluid build-up in the lungs. Moderate concentrations can cause more severe irritation of the eyes and respiratory system, while high concentrations of H2S can result in immediate collapse and loss of breathing, with a high probability of death. A lethal dose for 50% of the human population is an exposure of just 1112 mg/m3 (800ppm)7 for a period of five minutes.
H2S is also corrosive and highly flammable and can be explosive when mixed with air. The risk posed by the gas is greatly exacerbated by the fact that it’s denser than air, which means it tends to collect close to the ground in poorly ventilated areas.
H2S occurs naturally in crude petroleum and natural gas; and is produced practically anywhere elemental sulfur comes into contact with organic material, especially at high temperatures. This means that petroleum drilling and processing, sewage treatment, and agriculture are all sources of H2S.3 It is a problem for several other industries: it’s a common byproduct in paper manufacturing, and in the construction industry it can be released during excavation work in swamps or old landfills. Any manufacturing facility that uses iron smelters or coke ovens may also produce H2S as a byproduct. Reliable detection of H2S is important for many industries.
Modern gas detectors are capable of very accurately measuring H2S concentrations in the air.4 Installing permanent gas detectors in high-risk areas and equipping personnel with portable gas monitors means that facilities and personnel are easily protected.
Making sure gas detectors are calibrated and tested is essential – this is especially true for H2S, given the significant risks associated with it. Users should be aware of the health hazards when bump testing and calibrating H2S detectors. Tests are carried out with low concentrations of H2S, generally supplied in disposable canisters. Since H2S is corrosive, it’s recommended that a stainless steel regulators are used along with compatible tubing.5
Multi-gas detectors are increasingly affordable and versatile: some portable gas detectors are capable of measuring as many as seven different gas components simultaneously.
Of course, gas detectors alone cannot save lives if they’re not properly maintained and used. Virtually all gas detectors are prone to “drift”, a loss of accuracy due to environmental effects and age. All non-disposable gas detectors must be calibrated regularly to ensure that they are working properly. Multi-gas detectors contain multiple sensors for different gases, all of which must be calibrated: this can make calibration particularly time consuming. Fortunately, the time and effort required to calibrate a multi-gas sensor can be drastically reduced by using a multi-component calibration gas mixture. Using a multi-component reference gas mixture makes calibrating a four- or five-gas detector no more time consuming than a single gas detector.
Air Products provides H2S reference mixtures in precise concentrations to ensure that bump/calibration tests of this dangerous gas can be carried out as accurately and safely as possible.6 Our portable non-refillable canisters are available in a range of sizes to ensure the perfect combination of volume and portability for all your testing requirements.
"Our business relies on simple bump testing of gas detectorson board marine vessels. Complex high pressure cylinders and regulators would make the job too difficult but we find the Air Products non-refillable offerings very easy to use and the equipment is simple to operate."
"We are involved in the installation, commissioning and maintenance of a wide range of gas detection equipment into many market sectors. The fact that the Air Products’ range covers all of the flammable, toxic, quad-gas and corrosive gas requirements for this market is very important to us."
"Personal, portable and fixed gas detection equipment is widely used in many safety critical applications and these items are often subjected to relatively harsh environments and working conditions. The gas sensing element within this equipment is perhaps the most fragile and crucial component, and if this was to fail, it would render the equipment useless. The selection of appropriate test gas is important to ensure the bump test is carried out correctly and as an active member of CoGDEM, Air Products know about it. They have contributed to the CoGDEM Guide to Gas Detection, a new hardback reference book which explains best practice and aids the selection of suitable test gases and equipment."