Most heaters have thermostats to cycle them on and off to maintain a preset temperature.
Most will also have a separate "thermal fuse" that will melt, opening the power circuit, if the thermostat fails, or the heating element exceeds its design temperature.
There is usually a bi-metal switch, either auto reset or manual reset, or both. The auto reset would switch off at a lower temperature than the manual reset.
There are also fusible links which melt at a specific (or near enough) temperature.
These require replacement and can not be reset.
heaters rely on external devcie to turn them off when temperature increases over certain limit.
heaters themselves have little own protection (resistance increases with temperature, thus reducing current and curbing temperature rise)
http://en.wikipedia.org/wiki/Thermal_cut...
i mean to say how a fan heater cutoff itself to protect it from damage is it sometype of mechanical switch or something else and how it works
