What is FFD "Flame Failure Device" or FSD "Flame Supervision Device" ?

What is FFD (Flame Failure Device) or FSD (Flame Supervision Device)?

A Flame Supervision Device (or FSD) or Flame Failure Device (FFD) is a part of the gas burner system that ensures that the fuel supply to a gas appliance such as a gas hob is cut off automatically and immediately if for any reason the flame goes out or becomes unstable.

This device is a legal requirement on all cookers sold in the Republic of Ireland.

The technical terminology for the Flame Failure Device is a Thermo-Couple.