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Health & Safety Executive release safety notice on hydrogen sulphide (H2S) in cargo and slop tanks

05 May 2023

The UK Health & Safety Executive has issued a safety notice after identifying high concentrations of hydrogen sulphide (H2S) in ullage spaces of cargo and slop tanks. The safety notice, issued on 23 April, is aimed at operators of floating production storage and offloading (FPSO) and floating storage and offloading (FSO) vessels and floating storage units (FSU) in the UK continental shelf (UKCS).

In the notice, the HSE says the high concentrations identified (up to 16,000ppm) are above the upper measuring limits of the standard portable gas monitoring equipment generally used onboard tankers and floating production storage and offloading (FPSOs), and may be undetected.

Hydrogen sulphide concentrations over 1,000ppm can cause immediate collapse with loss of breathing, even after inhalation of a single breath. This corrosive gas can also pit and corrode steel, which can affect the integrity of cargo containment systems and hull structures.

Duty holders operating FPSOs and floating storage units (FSUs) must regularly monitor ullage spaces of cargo and slop tanks for the presence of toxic gas such as hydrogen sulphide, using appropriate equipment.

If detected, duty holders must ensure that the installation has adopted and implemented a suitable hydrogen sulphide management process in accordance with HSE's information sheet, Managing hydrogen sulphide detection offshore.

View the safety notice for full details

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