When choosing a control system for your facility, there are many factors to take into consideration including system reliability (translated into plant uptime), upkeep and maintenance costs, installation costs, compatibility with installed control systems, quality of support from manufacturers, etc. But what about process safety? When is it necessary to choose a Safety Instrumented System (SIS) instead of a Basic Process Control System (BPCS)? And what do these two terms mean? In this article, we explore these questions.