Providing a highly safe tool for preparing samples for elemental analysis of Halogens, Phosphorus and Sulfur using the oxygen flask combustion procedure, the Model OFCU-1 is capable of being used for repeatable determination of elemental composition from percentage levels to parts per million. The oxygen flask combustion procedure is provided as the preparatory step in the determination of bromine, chlorine, fluorine, iodine, phosphorus and sulfur in some Pharmacopeial articles. Combustion of the material under test (usually organic) yields water-soluble inorganic products, which may be analysed for specific elements as directed in the individual Pharmacopeia monograph or general chapter.