We have a raised floor in the finished room of the basement of our 80-yr-old house. The floor is pine covered with carpet and appears to be raised about 3-4". There are several vents through the basement, with metal vent covers. When I remove the vent covers, I seem to be looking directly at the ground! Should I be concerned about this? A masonry guy who was doing some work here told me the floor is built exactly like it should be, with the vents for moisture balance and air flow. Just wondering if he is right. Thanks for your help.