 The method was further refined within the company, under the name "operability studies", and became the third stage of its hazard analysis procedure (the first two being done at the conceptual and specification stages) when the first detailed design was produced.In 1974 a one-week safety course including this procedure was offered by the Institution of Chemical Engineers (IChemE) at Teesside Polytechnic.Coming shortly after the Flixborough disaster, the course was fully booked, as were ones in the next few years.