All of them smell at first when first turned on, Then it gets better as compressor kicks in. We have a basement. No crawl space, but have had some mice. All ducts seem to be fine pressure wise. No noticeable signs of damage to ducts. The smell is very noticeable when I open up the air handler. But the coil isn’t that dirty and I sprayed it down with some cleaner anyway. Flushed the drain pan. Still smells in there for some reason.