SENIOR staff at China Light and Power have ordered a review of procedures following an explosion at one of their chemical manufacturing plants. The blast happened at Tsing Yi power station on November 24 but news of it has just been made public. Ironically, it occurred the day after the jury at the resumed inquest into the deaths of two workers in the Castle Peak power station explosion last year returned new verdicts of death by lack of care. And in another coincidence, it involved the same gas. The latest explosion occurred at a part of the complex which is used to produce sodium hypochlorite, an unstable compound which in dilute form is used in the manufacture of household bleach. China Light and Power adds the chemical to sea water which is then used as a coolant for its power station turbine generators. Sodium hypochlorite kills marine life which might otherwise clog the machinery. Nobody was injured in the explosion, which occurred when a spark from a welding machine ignited highly flammable hydrogen, a by-product of the manufacturing process. The hydrogen is released through pipes into the atmosphere. It is thought that because of the prevailing weather conditions the spark was blown into the pipe. ''There was a loud thump. It caused mimimum damage to the pipe. There was no danger to the power plant and no interruption of power supplies,'' said CLP spokesman Dominic Tai Kuen-kwan. ''There were no harmful consequences. We reported all minor and major incidents to the authorities. We alerted the fire services in this instance. ''All procedures will have to be tightened up to ensure welding work is carried out with care, but I think it was a fluke accident. ''We keep very stringent safety control measures at all our power stations. Our safety record is very high among Hong Kong companies - we have one quarter of the average number of industrial incidents in the territory.'' The Castle Peak power station explosion was caused when pressurised hydrogen was mixed with air. In this incident, according to Mr Tai, the gas was not pressurised. CLP say they are examining what lessons need to be learned from the incident to prevent it from happening again with potentially more hazardous consequences. At the resumed inquest into the deaths of the two workers at Castle Peak, the jury was given information from two company reports into the cause of the blast which were not presented at the initial inquest. This new information contributed to the original verdicts of accidental death being overturned in favour of a verdict of death caused by lack of care. One of these confidential documents, known as the Blue Report, described the knowledge of CLP staff regarding the handling of contaminated hydrogen as ''extremely limited''. Mr Tai said no such confidential documents were being drawn up regarding the latest explosion.