FAST food fans could be risking their health because many leading makes of microwave oven do not kill harmful germs, it was revealed yesterday. Of 18 models tested, six could not heat up chilled meals above 70 degrees Celsius - the temperature needed to eliminate bacteria such as salmonella and listeria. The survey found guidelines on all 18 makes underestimated the time needed to heat food. Cooking times on 11 ovens were out by more than eight per cent and on one Whirlpool model the difference was nearly 21 per cent. The Consumer Council, which carried out the survey, called on manufacturers to redesign their microwaves. Medical Association vice-president Dr David Lee Ka-yan said it was vital chilled foods were heated to a minimum of 70 degrees Celsius. He said: 'Do not swap convenience for gastroenteritis. 'Germs can still grow on food if the refrigerator is not cold enough. If you reheat the food and the temperature is not high enough or you do not heat it for long enough you can easily get food poisoning.' The models that failed the temperature test were the Turbo DMR-622, Whirlpool 603 and 614, Imarflex MOC-2459, Moulinex D30 and the 240V National NN-5252. Consumer Counsel researcher Brian Cheng Yeuk-nin said one reason for the misleading cooking times was that many of the microwaves were aimed at the European market where the voltage was different. He said: 'The problem is Hong Kong uses 220 volts, but Europe uses 230 or 240 volts. There are no safety problems, but the microwaves just do not perform as well here. 'They should redesign them or make adjustments to the power supply.'