Evey now and then when I use my gas cooker (like now) there's a smell coming off it which is not gas but more of a paraffin type smell. Currently I have the oven and one of the rings going, have been for about half an hour and the smell is very noticeable. It's obviously not a gas leak or I woldn;t be writing this! Any ideas? We have gas central heating but it's only ever when the cooker is on and then only sometimes.