A MEETING at a Tai Po compact disc factory yesterday to review the handling of chemicals was interrupted by a chemical accident on the factory floor. Eighty workers were evacuated at Sonopress Panasia and four were taken to hospital. The management had been meeting to discuss safety measures prompted by this week's accident at the Hong Kong University of Science and Technology which led to the death of a student. After yesterday's incident, scientists said the two chemicals - one a very corrosive acid and the other an organic solvent - could have exploded, depending on the quantities mixed. The four employees were admitted to the Prince of Wales Hospital in fair condition after inhaling fumes from two chemicals accidentally mixed together. A worker who had been at the plant for about a week was refilling a container of the solvent, the colourless liquid methyl isobutyl ketone, but poured concentrated nitric acid in by mistake. Toxic fumes of nitric oxide - a very irritating gas that attacks the nose, mouth and throat - sent workers coughing out of the factory. The fumes spread from the ground floor laboratory and the managers' meeting was alerted. About 40 staff members were evacuated from the three-storey plant as police blocked a section of Dai Hei Street, and evacuated another 40 workers from a neighbouring building. A company spokesman said: 'After this incident, we have to put in extra measures to prevent it happening again.' And chemist Lam Hon-kong at the Government Laboratory said the workers were 'very lucky'. 'It could have caused a severe explosion because the concentrated acid would generate a lot of heat as it oxidised the solvent, which is volatile and flammable.'