Deaths due to hydrogen sulphide on a jack up rig at Bombay High: an avoidable accident

An enclosed space is an area with poor or no natural ventilation which is not designed for continuous occupancy, where access is limited and which may contain a dangerous atmosphere. Enclosed space atmospheres can be hazardous due to one or a combination of the conditions which includes oxygen deficiency; presence of toxic and/or flammable gases. When it is intended that personnel should enter or work in an enclosed space, care should be taken to create and maintain safe working conditions. The case report describes an incident on board an oil rig where the rig workers were exposed to noxious gases resulting in multiple fatalities. Work involved gas sampling/monitoring at various locations inside the "spud tanks" of the rig and certifying it free of noxious gases for marine surveyor's inspection. Contributory factors that have been frequently identified following enclosed space accident investigations are non-compliance with procedures, inappropriate equipment, poor supervision, complacency and over familiarity leading to short cuts being taken, detection and monitoring equipment not used or not working properly and improper action in an emergency. Preventive measures to avoid such accidents and create a safe working area are discussed.