MOST Tsing Yi Island residents would have to stay on the island even if there was an explosion at one of the hazardous installations. After meeting with Security Branch officials, Tsing Yi Concern Group spokesman Ting Hin-wah quoted Principal Assistant Secretary for Security, Frankie Lui Kin-fun, as saying that it was impossible to evacuate all the 170,000 Tsing Yi residents in a few hours. Mr Lui said only residents who lived in areas affected by an explosion would be evacuated, but Mr Ting had said the chance of a serious explosion was rare. Despite the Shenzhen explosion, the Government maintained that it would not disclose the emergency plan, Mr Lui said. But areas designated as shelters would be made public when an explosion occurred, he told the group. Mr Ting was dissatisfied that Mr Lui used ''economic considerations'' to ward off demands to move the installations off the island. Kwai Tsing District Board Chairman Leung Kwong-cheong urged the Government to devise a plan which could evacuate all residents when a large-scale explosion occurred, as suggested in the 1989 Tsing Yi Risk Reassessment Study. A temporary guideline specified in the report - that the storage capacity of hazardous installations with poor equipment be limited to 35 to 60 per cent - should be enacted, Mr Leung said. He doubted whether the Security Branch could handle large-scale explosions because Mr Lui seemed ignorant of the detailed plans to control a blaze in the installations, and did not even know about the 1989 study. The Government report was released in April 1989 after a gas leak at a Gulf Oil depot on the island in February 1989.