It is often necessary to replace the covers or "registers" after they corrode or become dirty. The registers are cleaned by blowing or brushing. Because metal registers are likely to rust or peel in the future, we do not recommend washing them. At this point, replacing the registers becomes a simple task. Replacements are available for about $10 to $20 at most home improvement stores. All you have to do is match the size. Make sure the louvers face the right direction. Clean air ducts reduce the number of airborne contaminants INSIDE the system.