Abstract: A marking element is disclosed for indicating whether a predefined temperature condition has been maintained. The marking element has a first material capable of flowing when exposed to a temperature above a predefined temperature separated from an absorbent second material by a heat-disruptable barrier layer. The first and second materials are such that when the heat-disruptable barrier layer is punctured and the predefined temperature is exceeded, the first material flows into the absorbent second material to produce a detectable change. The heat-disruptable barrier layer is formed of a heat-disruptable material associated with an element capable of being inductively heated by electromagnetic energy to effect disruption of such layer, thereby activating the marking element.