The polluting potential of petrol-powered engines used in tools such as chainsaws is significantly underrated. But the US Environmental Protection Agency (EPA) and California state regulatory authorities have started cracking down on these. To meet the EPA norms, Illinois-based Deere & Company has come up with an engine design that will not only cut emissions by up to 75 per cent but also cut down fuel consumption by up to 30 per cent. The new design adds an injection tube and nozzle to compress and re-route fuel and hot gas between the combustion chamber and the crankcase. This cuts down the amount of unburnt fuel that is released ( New Scientist , Vol 161, No 2174).