The higher temperature Isotech Blackbody Fixed Point Cells consist of high purity metals within a graphite body. Graphite reacts with air to form Carbon Dioxide. The rate of the reaction is temperature dependant. The effect is small at low temperatures but increases at higher temperatures. For Indium and Tin cells the effect is small and for Indium, Tin and Zinc cells in general no attention needs to be made. Yet for Aluminium, Silver and Copper Cells the oxygen must be excluded or the cells would be quickly damaged. The Model 984 Gas Flow System connects between an inert gas supply, such as Argon or Nitrogen and the Cell in its apparatus. The Model 984 has a regulator and a flow meter optimised to easily set the flow to 0.2 L/min and features an audible alarm should the gas flow be interrupted.