A Flame Supervision Device (FSD) is a safety mechanism used in gas appliances to monitor the presence of a flame. If the flame goes out unexpectedly, the FSD automatically shuts off the gas supply, preventing potential hazards such as gas leaks or explosions. This device is essential for ensuring safe operation in appliances like boilers, water heaters, and gas stoves. FSDs are commonly found in various types of gas equipment, including those used in residential and commercial settings. They are designed to comply with safety regulations and standards, making them a critical component in the safe use of gas-related technologies. Proper installation and maintenance of an FSD are vital for optimal performance and safety.