The ERA99-A is a robust, portable radiation environmental alarm designed to give a visible and audible indication of environmental radiation. Operation is by means of sealed push buttons. “ON” activates the unit to its standby position, indicated by an AMBER flashing beacon. In the event of exposure to radiation, the unit will automatically switch to a RED flashing beacon and give an audible tone. Depressing the “PRE-WARN” button causes a continuous audible tone. The “OFF” button removes power from the unit and, if connected to a mains supply, the unit will automatically charge the internal battery from the built-in charger.