Barrier structure for furnishing, selectively and variously, penetration and fire-threat protection on the outside surface of a target structure. The barrier structure includes a high-elastomeric coating having an inner face bonded to such a surface, an exposed outer face, and, within this coating, at least one elastomeric layer region extending to the outer face, and containing an embedded distribution of intumescence elements. Basic variations of this structure include (a) an additional layer region which is formed with elastomeric-material including an embedded distribution of liquid-imbiber beads, and (b) an additional layer region which is formed purely of elastomeric material. The elastomeric material employed, and the embedded liquid-imbiber beads where included, react to liquid petroleum-based substances (1) to imbibe such liquid, (2) to swell in size as a result of such imbibing, and (3) to coagulate into a sticky mass.