Hi Tim,
The only thing I could suggest is a fixed temperature heat detector. Unfortunately they are marked as “not a life saving device” and are not meant to replace smoke alarms / detectors.
There are two types of heat detectors: one (fixed temperature) will only sound an alarm if the temperature rises above certain (pre-set) level and the second type (rate-of-rise) which responds to rising temperature over a certain period of time.
Just type “fixed temperature detectors” in Google for a list of available products.
