The control of gas flow in thermogravimetric experiments is essential to the success and repeatability of the experiments. The gas flows in Thermo Cahn Thermogravimetric Experimental Stations (TherMax 200, 300, 400 and 700) are in three directions. These gas flows in the Thermo Cahn TG instruction manual are called purge gas, reaction gas, and vent gas. The instruction manual refers to one other gas, which is furnace air. Since this gas is used only to cool the furnace, it will not be discussed along with the gases that are in contact with the sample or its by-products. Furnace gas however, does influence the thermal behavior of the sample. The gas flow diagram for these gases is detailed in Figure 1. The computer Controlled solenoid valves for controlling the gas

flow are shown also in this figure.