While many of the advantages of a concrete structure are subtle ones, there is nothing subtle about concrete's ability to resist the spread of a fire while maintaining structural integrity. By comparison with almost any other building material, the endurance of concrete in the face of a major conflagration is almost uncanny; long after other parts of a building have been reduced to smoking rubble the concrete walls and decks often will remain as stoic evidence of the integrity of this material. One such example is the 1972 fire that broke out in the Airkem-Oklahoma Company building. The fire started above the dropped ceiling in the general area of the heating unit and was fed by stored combustible materials that exploded early in the fire. Sometime thereafter a gas line leading to the heater ruptured and further intensified the conflagration by adding gas as another fuel. Despite this, post-fire inspection of the building disclosed a very small amount of spalling and only one minor longitudinal crack located about three inches above the bottom of each of two roof units. Even when fires rage for hours and some damage is sustained by concrete, repair is frequently both feasible and economical. A major fire in a petrochemical plant in Japan attained extremely high temperatures because of the high combustibility of the materials manufactured. The damage was repaired by shotcreting.