Our coleman gas manufactured home furnace has recently developed an odor that is present only when the fan is running. I have a cold so I cannot smell it but my wife says it is quite strong. The odor is only present in a couple of the rooms. All looks normal in the area of the furnace, and the filters are clean.

Could be a small animal got into the duct under the home. Smells are very difficult to find especially when you are not there to smell it. Also watch the flames when the blower comes on. If they move around or change appearance in the fire box/heat X area when the fan starts to run call for on site service to check for a defective heat exchanger.

Is it an electrical smell?