MERT Worldwide – Hydrogen Sulphide H2S Hazards

MERT Worldwide – Toxic Gas Hazards On Ships

The purpose of this post is to highlight the Hydrogen Sulphide (H2S) dangers present on-board. H2S is the chemical symbol for Hydrogen Sulphide, its heavier than air, it is an explosive gas and if large concentrations are inhaled or come into contact with the skin it can be fatal. In smaller concentrations over a longer period of time it may also be fatal. H2S smells like rotten eggs, you will lose all sense of smell very quickly therefore it is important to get to a clean air area immediately after smelling rotten eggs. If any members of the crew have come in contact with H2S then they need to decontaminate if exposed to 50 PPM or more by removing contaminated clothing and wash any concentrations off their skin. H2S casualty or patient must be on oxygen as soon as they are in a clean air area then seek medical care.

H2S hazards are present in bilges, especially if the bilge is not kept clean. The sewage treatment plant is another high risk area. H2S may be present in confined spaces (voids and fuel tanks). Any pipe-work that has had AFFF – Aqueous Film Foaming Foam pass through it and not been flushed with fresh water will with time build up concentrations of H2S as well. The oily water treatment plant is another high risk H2S zone.

H2S dangers and hazards can be mitigated by installing H2S detectors and early warning devices. Crew awareness and training, supported by a robust toxic gas standard operating procedure further mitigates the risk to crew. All crew -members need to be aware of the dangers of H2S and the high risk areas on-board.  They must be able to recognise H2S alarms and immediately escape.

The Royal Australia Navy – Had several cases of H2S poisoning when their ships first had Sewage Treatment Plants installed. The problem they had at that time was there were no H2S detection equipment fitted in high risk areas and the first time the crew realised something was wrong was when crew-members became ill.

In the early 1990’s – Contractors working in underground pipes in Auckland, New Zealand died from H2S poisoning.

News Paper Article November 2012 – “Two people are in a critical condition and 19 others have been injured after breathing in hydrogen sulphide following a chemical spill at a tanning warehouse in Whanganui, NZ. Emergency services were called to Tasman Tanning Company just before 5pm on Friday following a chemical spill. A Whanganui District Health Boards spokeswoman Sue Campion told NZ Newswire on Friday evening that two people are in a critical condition and are being flown to Wellington Hospital after breathing in hydrogen sulphide. Hydrogen sulphide – a colourless, poisonous and flammable gas – can damage lungs and affect breathing”.

Health Effects of Hydrogen Sulfide

H2S is classed as a chemical asphyxiant, similar to carbon monoxide and cyanide gases. It inhibits cellular respiration and uptake of oxygen, causing biochemical suffocation. Typical exposure symptoms include:


0 – 10 ppm Irritation of the eyes, nose and throat


10 – 50 ppm Headache
Nausea and vomiting
Coughing and breathing difficulty


50 – 200 ppm Severe respiratory tract irritation
Eye irritation / acute conjunctivitis
Death in severe cases

Prolonged exposures at lower levels can lead to bronchitis, pneumonia, migraine headaches, pulmonary edema, and loss of motor coordination.

MERT Worldwide – Keeping sailors safe by providing specialist on-board safety (SOS) training.

MERT Worldwide – Maritime Emergency Response Training

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