Rubber floor mats and their consequences

Citroën delivered the 2CV with rubber floor mats. We always take these floor mats out of the car because they promotes rust on the floor panels. No 2CV is really waterproof. Whenever it rains, more or less water will leak into the car. This water will end up under the floor mats, and since these mats are rubber, the water is trapped. The rubber prevents the water from evaporating. It will be constantly wet under the floor mats. Even after some weeks of dry heat you will still find moisture. The photo shows you the consequences. The only solution is a rug without a rubber coat on the bottom. So the water can evaporate.