petrol & paraffin tanks

If petrol or paraffin tanks are placed near an engine or heating appliance there'sa danger that they could give off flammable vapours, which if ignited could cause a fire or explosion. To reduce the risk of this happening, it's a good idea for your boat's petrol or paraffin tanks to be installed as far away as possible from an engine or other heat source. In any event, they must not be installed closer than 100mm (4ins) to the engine or any other heat source. [2.7]