sufficiently during astandard un test series 6 external fire test bonfire test can result in an unacceptable quantity of unburned explosive material remaining within the detonators after the test is complete the inventors have discovered that by protecting principally the explosive end of the detonator whilst leaving other portions of the detonator at least substantially unprotected by protector materials improved detonator u201c cook off u201d is achievable even when the protectors of the invention remain attached to detonators during the testing procedures in this way the portions of the detonator shell not covered by a protector permit the heat of a test fire to be conducted more efficiently to the explosive material in the base charge at the explosive end of the detonator thereby allowing it to burn or cook off more rapidly and or efficiently a more rapid cook off also helps to reduce burning or other consuming of the protector material by the fire so that a sufficient mass of the protector can be retained at the explosive end for sufficient time for the protector to provide the required protective function preferably the protector is designed to stretch onto and to fit tightly upon the explosive end of the detonator so that it can maintain its position and its protective function.