A hazard detector monitoring system comprises one or more smoke detectors each provided with an electronic device containing information unique to the detector so as to identify the detector. A testing device is located at the end of a pole and held adjacent the detector to read and write to the electronic device through a wireless communication link. The testing device causes the detector to carry out a predetermined operation and the result of the operation is read by the testing device from the electronic device using the wireless communication link together with the identity of the detector.