There are two methods for detecting fire from the presence of heat via thermal detectors;
1. Fixed temperature heat detectors operate when the ambient temperature increases sufficiently to predetermined level where the heat detector will operate; or
2. A rate-of-rise heat detector operates when the ambient temperature increases over time equal to or greater than the rate of change the detector was manufactured to operate.
We have waterproof types, which are suitable for use in highly humid environments such as kitchen, bathroom, and drying room.