Covers the design, construction, marking, performance and testing of five types of detector for 'rate of rise' and 'fixed temperature' applications. Performance is prescribed in relation to insulation resistance tests and thermal tests (22 degrees Celsius/min, 6 degrees Celsius/min, 2 degrees Celsius/min and 0.5 degrees Celsius/min), together with an instantaneous rise of 20 degrees Celsius or 30 degrees Celsius according to type. Tests for resistance to corrosion, shock, crushing, low temperature, voltage excursion and transient voltage are also included together with test for strength of screw threads and fixings. Recommendations on the selection of the type of thermal detector and on the application of fixed capacitors are given.