I have a furnace on the third floor of my house with ducts leading to the third and second floors. First floor and basement have radiators. I noticed a couple of weeks ago that when I turn on the furnace upstairs a rotting smell comes thru the ducts ! Last time I tried to get duct cleaners out here they said that they didnt have hoses long enough to reach !!(WTF?) I have a guest staying at my house from out of town in a couple of weeks and want to give him the top floor to stay in. What can I do????