Pharmaceutical facility cleanrooms are designed to reduce and control particle contamination and to minimize the ingress and retention of microorganisms. Such risks typically are easy to control in well-designed, modern facilities. But risk mitigation is more difficult in older facilities. There is no exact definition of what constitutes an aging facility (or what are sometimes euphemistically called legacy facilities). For example, a facility established 100 years ago to manufacture a simple tablet can continue to operate perfectly well with careful…