HONG KONG OXYGEN has admitted wrongly labelling medical gas delivered to hospitals last week, six years after a similar error led to the death of a patient at the Canossa Hospital. Staff at the United Christian Hospital and St Teresa's Hospital raised the alarm after discovering that cylinders labelled 'medical air' actually contained carbon dioxide. Health and Fire Services officials yesterday asked Hong Kong Oxygen to launch an immediate inquiry to discover how the 10 bottles were mislabelled. 'We are asking Hong Kong Oxygen to give a comprehensive, full, investigative report to the Department of Health and ourselves,' said Fire Prevention Bureau chief Lam Chun-man, whose department licenses gas storage. 'The label said 'air' but the cylinders were for carbon dioxide and the contents were carbon dioxide. 'They were delivered to hospitals and discovered by hospital staff.' In January 1989, restaurant critic Shirley Boyde, 55, died after receiving almost-pure nitrogen from a Hong Kong Oxygen bottle labelled 'oxygen'. Six months later, three pregnant women at the Caritas Medical Centre were given carbon dioxide from a bottle marked 'nitrous oxide', which was also supplied by the company. A Hong Kong Oxygen spokesman said changes the company had instituted after Boyde's death meant no patients were at risk from the latest mistake. Each gas had a specific valve design so that even if the label was wrong the gas could not be used incorrectly, said company secretary Janet Chong Pui-yee. Only four cylinders were reported to the Government, but all 10 bottles had been mislabelled. 'It had the right pin index valve, so there was no possibility of having the incorrect gas administered,' she said. 'We notified all the hospital pharmacies. We're investigating what happened. It will take two weeks or so.' The fault was discovered in four 0.9 litre bottles on Friday, but the Fire Services and Health departments were not notified until Saturday afternoon. 'I would think that the company should at least have informed us, but the first I heard was from the hospitals themselves,' said Mr Lam. 'There needs to be better communication.' Queen Elizabeth Hospital chief executive Dr York Chow said medical air was compressed sterile air used to power pneumatic drills and saws. Carbon dioxide was used in laparoscopic or keyhole surgery. 'We have to blow up the abdomen with air to distend it and, if we use an air that is flammable, when you use the electric cautery there is a risk of ignition,' he said. 'Medical air is 20 per cent oxygen, so there is a slightly higher chance of ignition.'