We have an outdoor deck which about 10 years ago we had covered with Butyl flooring. This is a kind of rubber compound which comes in a flooring grade thickness. Now when we walk on it a layer of black dust comes off on our feet and is tramped into the house, where it is difficult to remove from the carpet. In fact we have made the outside deck a no-go area Can anyone explain what is happening and what we can do about it?