There is provided a blast occurrence apparatus for indicating the occurrence of a significant and potentially injury causing blast overpressure. The apparatus comprises a base, a housing and blast indication means to provide a visual indication that a significant blast has occurred. A blast indication means may be implemented using a rupturable membrane or a layer of microencapsulated paint or dye material, dimensioned to rupture at the desired overpressure level. The device is configured to withstand acceleration or shock resulting from impact.