Abstract: Hydrogen sulfide （H₂S） is one of the main hazards involved with oil and gas exploration and development operations,posing significant risks to people and assets. A FSO unit was converted from an oil tanker,and no equipment modifications were made to reduce the risk of H₂S during the conversion. The concentration of H₂S in the cargo oil tanks of the FSO unit could reach up to 360 mg/m³ during the production process. To effectively manage and control toxic gas exposure risks and mitigate H₂S hazards,risk prevention and control design is conducted from multiple aspects,including the renovation and upgrading of the living quarter,configuration of H₂S detection systems and emergency escape breathing devices （EEBDs）,risk analysis of operational processes,H₂S protective knowledge training,and H₂S emergency drills,so as to ensure the safety of production and living.

Key words: H₂S hazards, H₂S control, floating storage and offloading （FSO） unit, conversion, risk