Dysprosium fluoride and dysprosium oxide are non-flammable. Dysprosium iodide and dysprosium bromide are used in high-intensity metal-halide lamps. Dysprosium carbonate, Dy(CO), and dysprosium sulfate, Dy(SO), result from similar reactions. Crystals of calcium sulfate or calcium fluoride are doped with dysprosium. Dysprosium titanate was undergoing evaluation for pressurized water control rods. The trivalent dysprosium ion (Dy) has been studied due its downshifting luminescence properties. Soluble dysprosium salts, such as dysprosium chloride and dysprosium nitrate, are mildly toxic when ingested. Dysprosium has a simple ferromagnetic ordering at temperatures below . Dysprosium halides, such as DyF and DyBr, tend to take on a yellow color. These compounds dissociate near the hot center of the lamp, releasing isolated dysprosium atoms. When these crystals are exposed to radiation, the dysprosium atoms become excited and luminescent. Dysprosium chloride fires, however, can be extinguished with water. Dysprosium is used in dosimeters for measuring ionizing radiation. Nanofibers of dysprosium compounds have high strength and a large surface area. Dysprosium and holmium have the highest magnetic strengths of the elements, especially at low temperatures.