Hi (hope this gets to those who responded initially to my query),

This is an update. It took a while but I finally did get my car back to the shop. My mechanic did detect a coolant leak near the thermostat which he replaced. It's a lot better but there still is particular and unwanted smell. And the fan still stays on for a long time, about an hour, after the engine has been turned off. Sometimes the fan doesn't start until an half hour or more after the engine has been turned off. Probably takes some time for the humidity to be detected.

So any more suggestions would be welcomed. My mechanic did check the carpet again and it is confirmed as dry. I also did spray Lysol into the vents. And I try to use outside circulation more often over recirculation (except when passing by the diesels).

Thanks