The following case is reported by the Union of Chemical Industry in 1907: Three plumbers who were employed on the night shift in a chemical factory and had gone to sleep in a workroom were found in a dying condition two hours later. In the factory barium sulphide solution in a series of large saturating vessels was being converted into barium carbonate by forcing in carbonic acid gas; the sulphuretted hydrogen gas evolved was collected in a gasometer, burnt, and utilised for manufacture of sulphuric acid. In the saturating vessels were test cocks, the smell from which enabled the workers to know whether all the sulphuretted hydrogen gas had been driven out. If this was so the contents of the retort were driven by means of carbonic acid gas into a subsidiary vessel, and the vessel again filled with barium sulphide liquor. From these intermediate vessels the baryta was pumped into filter presses, the last remains of sulphuretted hydrogen gas being carried away by a fan into a ventilating shaft. The subsidiary vessel and ventilating shaft were situated in front of the windows of the repairing shop. On the night in question a worker had thoughtlessly driven the contents out of one saturating vessel before the sulphuretted hydrogen gas had been completely removed, and the driving belt of the fan was broken. Consequently, the sulphuretted hydrogen gas escaping from the subsidiary vessel entered through the windows of the workshop and collected over the floor where the victims of the unusual combination of circumstances slept. In another chemical works two workers suffered from severe poisoning in the barium chloride department. The plant consisted of a closed vat which, in addition to the openings for admitting the barium sulphide liquor and sulphuric acid, had a duct with steam injector connected with the chimney for taking away the sulphuretted hydrogen gas. Owing to a breakdown the plant was at a standstill, as a result of which the ventilating duct became blocked by ice. When the plant was set in motion again the sulphuretted hydrogen gas escaped through the sulphuric acid opening. One of the workers affected remained for two days unconscious.[1]