We put in a new Comfortmaker gas-pack downstairs unit last fall. It worked great during the winter. When we turned the air conditioner on this spring we noticed an unusual odor. My wife says it smells like steelwool or grease. It reminds me faintly of WD40. The installer returned and sprayed some chemicals to kill mold although he said he did not think that was the cause of the odor. He said he had never smelled the odor before. A week later the odor continues. It is strongest when the fan is blowing and the AC is off. It also seems to be stronger on days that are cloudy and raining. The strongest odor seems to be in the hallway next to the return vent. When the installer came before he entered the house, he opened the unit and the odor was easily detectable. After charging $100. for the visit, he suggested that we contact a cleaning company and have them clean our duct work. Any ideas? Is it the new unit or could it be the ductwork or something else? Help and many thanks.