Hydrogen sulphide (H2S) is a colorless gas that burns with a pale blue flame in air. It is moderately soluble in water and rapidly converts to sulfur dioxide in the atmosphere. H2S acts by inhibiting cytochrome oxidase and depressing the respiratory center in the brain. Occupations associated with H2S poisoning include carbon disulfide production, sewer work, petroleum production, and mining. Acute exposure can cause rapid breathing, nausea, vomiting, loss of consciousness, and death if not resuscitated. Chronic exposure causes no effects except for an unpleasant smell, which can be a nuisance. Treatment involves symptom relief only, as there is no specific antidote.

1. HydrogenSulphide (H2S)
Characteristics:- Colourless gas wgich burns in air with a pale blue flame. It is moderately
soluble in water. It is rapidly converted to Sulphur Di Oxide in the atmosphere by a reaction
with Hydroxyl Group & Carbonyl Sulphide. In the body the sulphide ions are oxidized to Thio
Sulphate & Sulphates in the liver & Kidneys & mostly eliminated in the urine. It is a chemical
asphyxiant & it’s smell is just like rotten egg.
Mechanism of Action:- It acts through the Inhibition of Cytochrome Oxidase as well as through
a direct depressant effect on Respiratory Centre in the brain.
Occupations Associated With H2S Poisoning:- 1) Carbon Sulphide Production 2) Viscous
Rayon Production 3) Sewer & Tunnel Workers 4) Petroleum Production &
Processing 5) Mining 6) Pulp Industry 7) Sulphuric Acid Production 8) Glue
Manufacture
Toxicity:- A) Acute:- 1) RapidBreathing& DistresswithNausea&Vomiting
2) These maybe rapidly
followedbyLossof Consciousness,usuallyinassociationwithcessationof
breathing.
Loss of Consciousnesswithoutwarningcanoccur on suddenexposuretoa high
concentrationof H2S (more than200ppm) afteronlyone or twobreaths,known
as “ KnockedDown” & there is highpossibilityof Death,unlessEmergency
Resuscitationiscommenced.
3) It isa PulmonaryIrritant&may cause NonCardiac PulmonaryEdema.
4) Conjunctivitislike symptoms
B) Sub Acute:-1) KeratoConjunctivitisusually the featuresof subacute toxicitycharacterized
By a) Blepharitis b) IrritantConjunctivitis c) Lecremation
d) Photophobia e) Sensationof Grittiness&Paininthe eyesassociatedwith
Superficial Punctate Corneal Erosion.
2) Some victimssufferfromnonspecificsymptomslike a) Hypersucceptebility
of gas smell. B) fatigue c) PoorMemory d) Irritability e) Disturbance of
Equilibrium
C) Chronic:- Nothingexceptunpleasantsmell canbe a considerablenuisance.
As perWHO Guidelines,ConcentrationLimitin Ambientlimitof Wateris7micro grams/M³
Treatment:- 1) No specifictreatmentexceptNitrite (Amyl Nitrate) maybe used,butremains
controversy.
2) Symptomatictreatment.
Rotten egg smell can be detected below 1 ppm. However, the sense of smell to H2S is soon lost
over 20 ppm. Therefore the worker may have very little warning of the presence of gas at
dangerous concentration.
Very VeryDangerous in rayon Industries
Eyes usuallyrecoverwithin 24 hours, after removal from exposure or
treatment withChloramphenicol Eye Ointment,but Corneal Ulceration&
Acute Keratitishave beenrecorded.