Flashovers - in which accumulated vapour in an enclosed burning area suddenly ignites with searing heat well above 500 degrees Celsius, creating strong pressure - are one of the greatest perils firefighters face. 'It's the nightmare of all firemen,' said Fire Services Department New Territories South divisional commander Szeto Yat-san, describing how the area surrounding a fire could suddenly become engulfed in flames. 'The build-up of heat triggers a flashover. It happens all of a sudden.' The chief of a firemen's union said the union would meet the department to discuss a review of firemen's protective gear. Alan Tsui Chi-keung, chairman of the Hong Kong Fire Services Department Staffs General Association, said that while protective suits could withstand heat of 800 degrees for 30 seconds, a human body could not. Fireman Wong Ka-hei, who died in yesterday's fire, suffered 20 per cent internal burns without any superficial skin burns, he said. 'When a flashover occurs, it will be 500 to 600 degrees Celsius,' he said. All firefighters were trained to combat flashovers, and one of the keys was not to pour too much water into an enclosed area, Mr Tsui said. 'Water can increase the amount of vapour which will help to maintain the intense heat inside the room,' he said. 'And most of all, we cannot anticipate the occurrence of a flashover.' When there was a flashover, the whole room would be filled with flames and air turbulence. 'If you are fortunate enough to find cover, your life can be saved,' Mr Tsui said. 'As far as we understand, the firefighters followed all the standard procedures in putting out the blaze. They were all equipped with sufficient gear and protection suits. The death of Wong was very unfortunate.' The department said cadet firefighters and serving firemen are sent to a smoke-filled simulator to deal with flashovers as part of training. The simulator, converted from a cargo container, could reach temperatures of about 600 degrees Celsius.