In the maritime industry we can be exposed to toxic vapours such as H2S released from many different sources including the cargo, bunkers and supplies we carry and the adhesives we use. The dangers of H2S are well known and yet precautions are often ignored and procedures are not followed.
In this blog I will be discussing 3 incidents which have been shared with me.
Incident 1
An oil tanker carrying crude oil with high H2S content was requested to reduce the H2S by venting to air. The vessel began venting during the night. In the early hours of the morning a number of crew members began complaining of headaches and dizziness.
The venting was immediately stopped. Investigation found that the accommodation air conditioning intake was not completely closed and a change in the wind direction caused the H2S vents to drift toward the air conditioning intake.
Incident 2
During a STS transfer between 2 crude oil tankers, the duty seaman started to feel a slight headache and reported the issue. Soon afterward, the vessel’s high H2S alarm sounded and cargo operations were immediately stopped. There were very light winds at the time which allowed the vapours from the loading vessel to settle on the decks of both vessels. The vessels moved to another location to carry out the STS transfer where the wind was carrying the vapours away from both the vessels. The seaman was not wearing a personal gas detector.
Incident 3
An offshore vessel had back loaded slops into a tank containing previous cargo. Due to the planning cycle the vessel carried the slops for a few days. When the vessel came to discharge the slops, a strong smell of H2S was noticed by the crew. A test confirmed that H2S was present well above the safe limit. Discharge of slops was postponed until H2S was lowered to acceptable levels. Laboratory test determined that H2S was generated in the tank due to chemical reaction between the cargo and slops.
Lessons Learnt
- Follow H2S precautions and procedures when carrying H2S content cargo or supplies (ref: ISGOTT 2.3.6.4 “Precautions for handling cargo and bunkers containing H2S”).
- Monitoring wind direction for changes that could affect vessel ventilation systems (ref: ISGOTT 11.1.9).
- Always wear your personal gas detector when the presence of H2S is possible even if the source may be from another location (vessel / platform).
Thank you.
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