Best way to remove moisture and mold in car?

I find it strange to have a moisture issue with something stored indoors. My 40x80 steel quonset is next to bone dry during all months of the year. It has 1 two foot square vent on either end of the building. Un heated,and weather here will reach near -40 on the coldest of days.

vehicle put into storage with wet carpet?
Or just a sealed storage building,and not properly ventilated?
The air-dry products are calcium chloride, corrosive and harmful if given the oppurtunity.
The charcoal suggestion seems a better alternative to me.
The issue of moisture still needs to be handled,or your car will rot from the inside out.