A method of responding to a condition in an exhaust ventilation system that has an exhaust hood includes receiving, at a control module, an exhaust air temperature signal representing a temperature of the exhaust air in a vicinity of the exhaust hood, the exhaust air temperature signal being generated by a temperature sensor. The method also includes receiving a radiant temperature signal representing a temperature of a surface of a cooking appliance that generates the exhaust air, the radiant temperature signal being generated by a radiant temperature sensor. Further, the method includes receiving a pressure signal representing the pressure in the hood and determining a state of the cooking appliance based on the received exhaust air temperature signal, the received radiant temperature signal, and the received pressure signal. Finally, the method responds to the determined appliance state by outputting a control signal from the control module.