Obscure question. I rent a garage for my GTO. It is cement block, has vents on the doors and on one wall, no windows. It has a stone floor over dirt, and the rocks sometime appear to be wet. There are other sign I may have a moisture problem. Taking steps to fix, with more vents in door, powered ventilation fan in roof and plastic vapor barrier under rock. I bought a hygrometer to measure the humidity. My quesrtion is, does anyone know what an acceplable RH is to keep a car in that enviroment without worry?