Abstract: A method of monitoring a feature of a blast such as velocity of detonation (VOD) comprises the steps of providing a detonator 16.1 at a blast site 12. Prior to the blast, a blast control signal path 20, 18.1 is utilized to communicate blast control signals to the detonator. During a period following start of the blast, a blast feature signal communication path 18.1, 20 comprising at least part of the blast control signal path is utilized to communicate a blast feature signal relating to the feature to a remote blast feature monitoring station 26. The blast feature signal is generated by generating a monitoring signal in a conductor arrangement 18.1 connected to die detonator, utilizing a sensor outside of the housing of the detonator to sense changes in a blast feature monitoring parameter of the monitoring signal, and transmitting data relating to the changes to the station 26.