Abstract: The invention relates to fire detector comprising a CPU and a sensor providing an analog measurement signal to the CPU. The CPU includes a non-volatile memory in which at least one normal value for the measurement signal and maintenance dates are recorded, the fire detector also including an interface giving access to the contents of the non-volatile memory without disassembling the fire detector. On each occasion that maintenance has been performed, a new maintenance date is recorded in the non-volatile memory. Nevertheless, such recordal is prevented if the measurement signal differs excessively from its normal value.