Hydrogen Sulphide

Formula: H₂S | CAS: 7783-06-4

Detecting hydrogen sulphide: Exposure at higher levels can result in death almost instantaneously

What is hydrogen sulphide gas?

Hydrogen Sulphide (H₂S) is a gas commonly found during the drilling and production of crude oil and natural gas, plus in wastewater treatment and utility facilities and sewers. The gas is produced as a result of the microbial breakdown of organic materials in the absence of oxygen. Colourless, flammable, poisonous and corrosive, H₂S gas is noticeable by its rotten egg smell. With toxicity similar to carbon monoxide, which prevents cellular respiration, monitoring and early detection of H₂S could mean the difference between life and death.

It is also used or is a by-product in many industrial processes such as:

• Petroleum production and refining
• Sewer and wastewater treatment
• Agricultural silos and pits
• Textile manufacturing
• Pulp and paper processing
• Food processing
• Hot asphalt paving
• Mining

Health effects following inhalation of high concentrations of hydrogen sulphide may include collapse, inability to breathe and death within minutes. A range of effects on the nervous and cardiovascular system may occur following single or repeated exposures to high hydrogen sulphide concentrations. Skin discolouration, pain, itching, skin redness and local frostbite may occur if skin is exposed to compressed hydrogen sulphide liquid. Eye exposure may cause irritation, inflammation, tearing, sensitivity to light and conjunctivitis.
– GOV.UK

Effects of Short & Long term exposure to hydrogen sulphide

SHORT TERM EXPOSURE: (ACUTE)
Gas is a silent threat, often invisible to the body’s senses. Inhalation is the primary route of exposure to hydrogen sulphide. Though it may be easily smelled by some people at small concentrations, continuous exposure to even low levels of H₂S quickly deadens the sense of smell (olfactory desensitisation). Exposure to high levels of the gas can deaden the sense of smell instantly. Although the scent of H₂S is a characteristic, smell is not a dependable indicator of H₂S gas presence or for indicating increasing concentrations of the gas.

LONG TERM EXPOSURE: (CHRONIC)
Those having prolonged exposure to high enough levels of H₂S gas to cause unconsciousness may continue to experience headaches, reduced attention span and motor functions. Pulmonary effects of H₂S gas exposure may not be apparent for up to 72 hours following removal from the affected environment. Delayed pulmonary edema and a build-up of excess fluid in the lungs may also occur following exposure to high concentrations.