You searched for: “pyrostat
pyrostat (s) (noun), prostates (pl)
1. A thermostat that operates at very high temperatures: There was a pyrostat integrated in the new stove Susan had which regulated the supply of heat she wanted to use for cooking.
2. An automatic sensing device that triggers an alarm or extinguisher if there happens to be a fire: The pyrostat started instantly when the flames broke out in the kitchen of Mary's house.