THE explosion which rocked the Tuen Mun flat, killing one and injuring eight others, was more intense than usual because of the type of gas connected to the building, the gas supplier said. The flat, one of 20,000 households still using substitute natural gas rather than Towngas, has now become the subject of close examination by fire and gas experts from the Government and the Hong Kong and China Gas Company which supplied the natural gas. A Hong Kong and China Gas Company spokesman said yesterday that Tuen Mun was the only area in Hong Kong with natural gas connected and that facilities to pipe in Towngas would not be in place until 1995. She said if Towngas rather than natural gas had been connected to the building, the blast would have been different. ''The explosion range or the area taken in by the blast is less with natural gas than with Towngas but the blast is more intense. The explosion power is higher in natural gas,'' she said. Substitute natural gas is a combination of LPG and air. Towngas is made up mostly of carbon monoxide, oxygen, methane and hydrogen. It is understood that natural gas is less toxic than Towngas which affects the nervous system because of the strong presence of carbon monoxide. Gas Standards Office assistant director Keith Whittle said people with natural gas connected should not be concerned about its safety. However, he said like all such gases it was dangerous if there was a leak and steps should be taken to avoid igniting gas in a situation where there had been a leak. ''Anything from using the telephone to turning on an electrical switch could spark an explosion, even opening a fridge would do it,'' Mr Whittle said. He said the strength of an explosion depended on the degree of confinement of the gas. ''In a room with no windows to give way to an explosion the force would be increased.'' Mr Whittle said residents of the 44-storey building where yesterday's blast occurred should not be concerned about leaks or problems because complete safety checks would be made before gas was reconnected. Safety inspectors from the Gas Standards Office were sent to the scene of yesterday's blast and will make reports for the Fire Services Department and the gas company. A gas fitting connected to the stove in the apartment had been loosened to assist in the rapid release of gas into the home.
