Abstract: A flame failure device has a hollow, tubular, heat-resistant, temperature sensitive member to be directly heated by a flame and so arranged that the member will expand or contract along a generally rectilinear axis as it is heated or cooled. The temperature-sensitive member is connected to a mount in a manner which permits or permitted at least initial adjustment of the relative position of the mount and temperature-sensitive element along the generally rectilinear axis and has an abutment which will move relative to the mount as the temperature-sensitive member is heated or cooled. A main valve for controlling supply of fuel to a burner has a fuel inlet, a fuel outlet, a chamber having a diaphragm defining a wall of the chamber, a main-valve member operatively connected to the diaphragm and movable therewith, and a supply passage for restricted fuel flow to the chamber.