To check on whether you need to refinish or just thoroughly clean older wood furniture, first try cleaning the piece a few times using a good furniture cleaner on a cotton cloth. Let it dry between tries. If the wood finish begins to clear, proceed with cleaning. If it remains dark, marred or alligatored, then refinish.
Pay special attention to carpet on concrete floors. Carpet can absorb moisture and serve as a place for biological pollutants to grow. Use area rugs which can be taken up and washed often. In certain climates, if carpet is to be installed over a concrete floor, it may be necessary to use a vapor barrier (plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem.