In numerous branches of industry heat-treatment and combustion processes play a decisive role during production and in the quality of the final product. These applications have one thing in common: Due to the high temperatures thermocouples are almost always used. Besides the non-precious-metal containing ones, mainly types E, J or L, K and N, platinum thermocouples types S, R or B are increasingly being used. These must be protected against contaminating, corrosive and/or abrasive ambient influences. Various designs with different protection tube materials are available for these applications.