Garbage had concealed the hole and prevented it from being filled with incombustible material. It also has rescue boats, an emergency generator, and incombustible furniture throughout the boat. In an electric arc, PCBs generate incombustible gases. In grate boilers, incombustible ash agglomerates as cinders through prolonged residential time. When coal is burnt, the incombustible clay particles are left behind as ash. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize.