Confined spaces: In aquaculture, confined spaces are found in association with feed silos/barge systems, pipelines, vessel holds, cold storage facilities and tanks. In addition to oxygen-deficient atmospheres, fatalities have resulted from the inhalation of hydrogen sulphide gas that had concentrated in the stagnant sludge water at the tank bottom. Multiple fatalities often occur when a worker(s), without any safety equipment, tries to rescue the fellow worker in difficulty, and is then also asphyxiated.