Electrical protective or emergency shutdown systems are utilized throughout the petrochemical industry for safety and to avoid severe environmental and/or economic events. Requirements for these critical systems are that they work every time, on demand, and do not initiate nuisance events. These requirements
were difficult to achieve in most early systems but the systems have improved over the years.
Emergency shutdown system design has been unregulated in the U.S., but new standards will require strict guidelines for design, application, documentation, and software testing and control.