A Safety Instrumented System (SIS) is a set of hardware and software designed to monitor and control industrial processes to prevent accidents. It operates by detecting hazardous conditions and taking action to mitigate risks, ensuring the safety of personnel and equipment. SIS is commonly used in industries such as oil and gas, chemical manufacturing, and power generation. The main components of an SIS include sensors, logic solvers, and actuators. Sensors detect abnormal conditions, logic solvers process the information and make decisions, and actuators implement safety measures. Together, these elements work to maintain safe operations and protect against potential failures.